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Ultrasound screening for familial ovarian cancer
CYNECOLOGIC
ONCOLOGY
43, 92-97 (1991)
Ultrasound Screening for Familial Ovarian Cancer THOMAS
H. BOURNE, MRCOG, MALCOLM I. WHITEHEAD, FRCOG, STUART CAMPBELL, FRCOG, PATRICK ROYSTON, M.Sc.,* VIJAY BHAN, MRCOG, AND WILLIAM P. COLLINS, D.Sc.
Academic Department of Obstetrics and Gynaecology, Kings College School of Medicine and Dentistry, Denmark Hill, London SE5 8RX, United Kingdom; and *Department of Medical Physics, Royal Postgraduate Medical School, Duane Road, London WI2 ONN, United Kingdom Received February
We have used transvaginal ultrasonography to screen 776 asymptomatic women for familial ovarian cancer. Every woman had at least one first- or second-degreerelative develop the disease (677, 87%; and 98, 13%, respectively). The mean age of the study population was 51 years (range, 24 to 78 years); 52% were premenopausal, 36% were naturally postmenopausal, and 12% had undergone a hysterectomy. Overall, 43 women (5.5%) were referred for surgical investigation and 39 had a laparotomy. Nineteen/thirty-nine (48%) had bilateral ovarian masses,and 15% of abnormal ovaries had more than one type of histopathology. Twenty-three tumors and thirty-two tumor-like conditions were detected. There were 3 casesof primary ovarian cancer (prevalence, 3.9/1000), all FIG0 stage Ia. None of the women has developed ovarian cancer within the first year of the scan (giving a provisional detection rate of 100%). The false positive rate was 40/773 (5.2%), the predictive value of a positive screen result was 7.7%, and the odds in favor of finding any massat laparotomy were about 19 to 1 or for any tumor, 1 to 1. At surgery the odds against fmding primary ovarian cancer were 12 to 1. The positive predictive value of the screening procedure and the prevalence of the disease were signiIicantIy higher than the corresponding values from a previous population-based screening program. 0 1991 Academic
Press, Inc.
INTRODUCTION
28, 1991
Previously we have evaluated the use of transabdominal ultrasonography as the first stage of a screening procedure for ovarian neoplasms in a general population [33. Other workers have reported data on the use of transvaginal ultrasonography for the same purpose [4]. Furthermore, preliminary results have shown that the combined use of transvaginal ultrasonography with color flow mapping and blood flow analyses might be used to distinguish malignant ovarian tumors from many types of benign masses [5,6]. The low incidence of ovarian cancer in the general population means that a multicenter clinical trial is required to evaluate the potential usefulness of these new techniques in a screening procedure for asymptomatic women. An alternative approach is to study women who are at a higher risk of developing the disease. Previous reports of families with several affected relatives, and the results of case-controlled studies and one prospective study, have suggested that a family history of ovarian cancer is an important risk factor for the disease [7-141. Accordingly, we are now studying a cohort of women who have had at least one close relative develop ovarian cancer. This report is concerned with the prevalence of primary cancer and other ovarian masses in the women who have been screened to date, and an evaluation of the first stage of the screening procedure.
Ovarian cancer is an insidious and intractable disease. The incidence in the United States increases with age to about 50 casesper 100,000 women per year (about 20,000 SUBJECTS AND METHODS new cases are reported annually) [l], and the cumulative The aim was to screen about loo0 self-referred, asymprisk up to the age of 75 years is 1.3%. Currently less than 30% of primary cancers are confined to the ovaries at tomatic women (age >25 years) who had had at least one the time of diagnosis (i.e., at FIG0 stage Ia or Ib), and close relative (i.e., a mother, sister, daughter, maternal the overall survival rate is less than 30%. Consequently, or paternal grandmother, or aunt) develop ovarian canthere is a need for an effective procedure to detect early cer. Potential volunteers were made aware of the study ovarian cancer (before metastasis has occurred), when by advertisements placed in the local and national press. the survival rate after surgery alone may be greater than All women who requested further information were sent details about the aims of the study, the screening pro90% [2]. 92 0090-8258191$1.50 Copyright 0 1991 by Academic Press, Inc. All rights of reproduction in any farm reserved.
ULTRASOUND
SCREENING FOR FAMILIAL
cedure, and the action to be taken if an abnormality was detected. The protocol was approved by the Research Ethics Committee of King’s College Hospital. A research nurse constructed a family pedigree from the information provided by each woman. A death certificate or hospital report was required to confirm that the close relative (i.e., the index case) had been diagnosed as having ovarian cancer or had had the disease at the time of death. Volunteers completed a questionnaire designed to provide epidemiological data and a relevant personal medical history. The women were classified as being either premenopausal (a menstrual period within the previous 12 months), naturally postmenopausal (age greater than 35 years and at least 12 elapsed months since the last menstrual period), or artificially postmenopausal (due to hysterectomy but with conservation of at least one ovary). Each screening consisted of one or more ultrasound examinations (scans) by the sequential use of transabdominal and transvaginal probes. The women were instructed to drink a liter of fluid 1 hr before being scanned transabdominally. Both ovaries were located and examined in the transverse and longitudinal planes with a Diasonics SPA 1000 scanner (Diasonics Sonotron, Bedford, UK) using a 3.5-MHz transducer. A morphologically normal ovary gave an image with a smooth ovoid outline and a uniform low-level echogenicity similar to that of the myometrium. Structures resembling normal follicles or corpora lutea in premenopausal women were noted in relation to the first day of the last menses. The maximum transverse (D1), anteroposterior (&), and longitudinal (&) diameters of both ovaries were measured. Ovarian volumes were estimated according to the formula volume = (7r/6 x D, x D2 x D-,). The women were then asked to empty their bladders before being scanned transvaginally in the lithotomy position with a 7.5 MHz transducer [5]. The probe sector angle was 110” and offset 15” to provide a good view of the reproductive organs. The probe was covered with a coupling gel, then a condom, and finally with more gel before insertion into the vagina. The ovaries were located adjacent to the internal iliac vessels, which appeared as anechoic tubular structures with echogenic walls. All observations and measurements were recorded. At each screening the result of a scan was regarded as positive if there was any sign of abnormal ovarian morphology (i.e., areas of hyper- or hypoechogenecity) [3]. Enlarged ovaries with no signs of abnormal morphology were regarded as normal. Women with a normal (negative) result on scanning were contacted 1 year later to check their health and arrange a second screening. Those women with an abnormal (positive) result were rescanned at intervals of 3 to 8 weeks to exclude transient changes in ovarian morphology or size. A volume reduction to less than 68% of that recorded at the initial scan usually
OVARIAN
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93
meant that the eventual screen result was regarded as negative [15]. Exceptions occurred due to adverse morphological changes in the contralateral ovary. If the result of the last scan was still positive the woman was informed about the nature and possible significance of the findings. The information was sent to the appropriate family doctor with a recommendation that the patient be referred to her local specialist or one at King’s College Hospital for further investigations involving laparotomy. Ovarian tissues removed at surgery were sent for histological examination. The stage of the disease was determined by the surgeon and the final diagnosis was based on the report from the histologist. Peripheral blood (10 ml) was taken at each stage of the screening procedure for the retrospective analysis of serum antigens. The ovaries were examined by transvaginal color flow mapping [5] for signs of vascular changes and decreased intratumoral resistance to blood flow at the time of the last scan. These data were also recorded for retrospective analysis. Both of these aspects of the study, and the relative merits of transabdominal and transvaginal ultrasonography, will be reported when sufficient data have been accumulated for statistical analysis. Histopathology
Tissues from abnormal ovaries were examined at the referral hospitals and histology reports were sent to the Ovarian Screening Clinic at King’s College Hospital. The masseswere classified according to criteria recommended by the World Health Organization [16]. The groups were common epithelial tumors, sex cord stromal tumors, germ cell tumors, and tumor-like conditions. The tumors were also classified as benign, borderline, or malignant. The stage of each primary cancer was determined from the surgical records according to the revised recommendations of the International Federation of Gynecologists and Obstetricians [17]. At stage Ia the tumor was limited to one ovary and the capsule was intact. In addition, there was no sign of the tumor on the external surface of the ovary and ascites was not present. Database and Statistical Analysis
A database was established using Foxbase running on an IBM PC/XT-compatible microcomputer with a hard disk. A tape streamer was used for data backup. A suite of programs was developed to facilitate data entry, checking, and retrieval. The detection rate (sensitivity) of the procedure was defined as the proportion of women with primary ovarian cancer who had a positive result on screening. This criterion could only be ascertained within the limitation of the study design, because there is no independent (reference) method to detect early ovarian cancer without resort to surgery. The false-positive rate
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BOURNE ET AL,
had one ultrasound scan; the remainder (118, 15%) had two to five repeat scans. All abnormal findings were observed by both transabdominal and transvaginal ultrasonography.
TABLE 1 Age and Menopausal State of the Study Population Age (complete years) Menopausal state
-39
Premenopausal 5.5 Naturally postmenopausal 0 Artificially postmenopausal 1 Total
40-49
50-59
60-
249
97
2
403 (52)
17
153
108
278 (36)
28
42
24
95 (12)
All
56 (7) 294 (38) 292 (38) 134 (17) 776 (100)
Note. The values are numbers (percentages) of women.
of the procedure was the proportion of women with a positive result on screening who were apparently free of cancer at the time of surgery (i.e., 100 minus specificity). The positive predictive value was the proportion of women with a positive screening result and ovarian cancer at surgery. The same data were expressed as an odds ratio, which was the chance in favor or against the presence of ovarian cancer at surgery in women with a positive screening result. RESULTS Subjects
The numbers of women (classified by age and menstrual state) are shown in Table 1. A total of 776 women were screened. Their mean age was 51 years (range, 24 to 78 years); 678 (87%) had at least one first-degree affected relative, and 98 (13%) reported a second-degree relative as the index case. Eighteen women (2%) had two firstdegree affected relatives. The mean age of the index cases at the time of death (or diagnosis if still alive) was 64 years (range, 25 to 94 years). Most women (658, 85%)
Outcome of Screening
The numbers of negative, initially positive/finally negative, initially positive/subsequently unknown, and initially positive/finally positive results are shown in Table 2 relative to the menopausal state of the women. Overall 5.5% of women had a positive screening result and were referred for surgical investigation. Higher proportions of premenopausal and artificially postmenopausal women had a positive/negative result than postmenopausal women. Nine women in the initially positive/subsequently unknown group (seven premenopausal, two artificially postmenopausal) are still awaiting a rescan (third to fifth), due to changes in morphology or volume between the two ovaries. Fifteen women are still awaiting a rescan (which has been delayed for personal reasons) and two have temporarily withdrawn from the study. There was a significantly higher proportion of positive/positive results in the group who had undergone an artificial menopause (x2 = 6.39, P = 0.01) than in the other groups. Forty-three women were referred for surgery; four underwent laparoscopy (at which time no ovarian abnormalities were detected), and thirty-nine (87%) underwent laparotomy and bilateral oophorectomy. Characteristics of Masses
A total of 1551 ovaries were screened (776 women), 78 ovaries were examined histologically (39 women), and 55 ovaries were abnormal (37 women). There was a high prevalence of bilateral masses (6/16, 38%) in premenopausal women, 5/12 (429’0) in naturally postmenopausal women, and 7/11 (64%) in artificially postmenopausal
TABLE 2 Results of Screening: Numbers and Percentages of Women in Each Menstrual State Result Negative
Positive/negative”
Positive/unknown
Positive/positive’
Menopausal state
No.
%
No.
%
No.
%
No.
%
Premenopausal Naturally postmenopausal Artificially postmenopausal
319 246
(79.2) (88.5)
46 11
(11.4) (4.0)
19 9
(4.7) (3.2)
19 12
(4.7) (4.3)
71
(74.7)
7
(7.4)
5
(5.3)
12
(12.6)
Total
636
(82.0)
64
(8.2)
33
(4.3)
43
(5.5)
” Result initially positive but abnormality had disappeared at rescan. ’ Patient referred for surgical investigation.
ULTRASOUND
SCREENING FOR FAMILIAL
OVARIAN
CANCER
95
TABLE 3 Histological Classification of Ovarian Masses Removed at Surgery Menopausal state Premenopausal
Naturally postmenopausal
Artificially postmenopausal
Total (%)
Epithelial Benign Malignant Sex cord, stromal Germ cell Tumor-like
3 2 0 3 14
8 0 0 0 8
5 1 1 0 10
16 (1.0) 3 (0.2) 1 (0.1) 3 (0.2) 32 (2.1)
Total
22
16
17
55 (3.5)
Type
” Of 1551 ovaries screened.
prevalence of primary ovarian cancer was 3/776 (i.e., 3.9 15% of abnormal ovaries. A histological classification, on per 1000) with a 95% confidence interval of 0.8 to II.3 the basis of the principal pathology of the abnormal ova- per thousand. ries removed at surgery, is shown in Table 3. Most per- Follow-up sistent masses were detected in premenopausal women, To date, one interval adenocarcinoma of the peritoand the majority were tumor-like conditions. Three welldifferentiated primary ovarian cancers, all FIG0 stage Ia, neum has been reported. The woman was 55 years old were detected (one serous cystadenocarcinoma, one cyst- and had not menstruated for 4 years. She contacted her adenoma of borderline malignancy, and one endometrioid family doctor about 11 months after the last scan and carcinoma). The women were aged 38, 63, and 54 years, described a 3-month history of abdominal pain and disrespectively; 2 were premenopausal and the other (the tension. Laparoscopy revealed the presence of dissemioldest) had undergone hysterectomy. The first woman had nated nodules in the peritoneum. A CT scan and a repeat a family history of site-specific ovarian cancer; the second ultrasonogram (at the referral hospital) showed that the had a first-degree relative with the disease but the family ovaries were apparently normal. Despite appropriate inpedigree suggested that it was a sporadic version of the vestigations the site of the primary tumor has not been disease. The third woman had a second-degree relative established. (maternal aunt) with ovarian cancer. DISCUSSION women. There was more than one type of pathology in
Evaluation
of Screening Procedure
The screening procedure had an apparent detection rate of 100% (within the limitation of the study design and our knowledge of the disease) with an overall false-positive rate of 5.2% (40/773) based upon the number of women with at least one ovary with a particular morphological abnormality. The false-positive rate for premenopausal women was 16/403 (4.0%), for naturally postmenopausal women 11/278 (4.0%), and for artificially postmenopausal women 19195 (10.6%). This difference is highly significant (x’ = 30.2, P = 0.001). Criteria for assessing the screening procedure are listed in Table 4. The odds in favor of a positive screening result being associated with any ovarian mass (by histological classification) were about 19 to 1, that is, 19 masses per 20 laparotomies. The odds fell to about 1 to 1 for the presence of any ovarian tumor at surgery, that is, 1 tumor per 2 laparotomies. The odds against the detection of primary ovarian cancer (from histological and folloti-up data) were 12 to 1, giving a probability of 1 in 13. The
To our knowledge this is the first report of a prospective study designed to assessthe prevalence of familial ovarian cancer and other pelvic masses,in a group of self-referred TABLE 4 AssessmentCriteria for the Screening Procedure
Ovarian pathology Any mass Any tumor Primary cancer
Detection rate (%> 100
Specificity (%)
Positive predictive value (%I
Odds”
94.8
94.9 51.2 7.7
18.6 to lb 1.0 to 1 12 to 1’
’ Calculated from results of laparotomy. b In favor of positive result on screening indicating the presence of each type of pathology; odds = positive predictive value/(100 - positive predictive value). c Against positive result on screening indicating the presence of each type of pathology; odds = positive predictive value/(100 - positive predictive value).
96
BOURNE ET AL.
women without specific symptoms of the disease. At interview most of the volunteers reported that a first- rather than a second-degree relative had developed ovarian cancer. The relatives most frequently quoted were mother (65%) or sister (25%). Most (87%) of the participants in the study were between 40 and 59 years old; 52% were premenopausal, 36% were naturally postmenopausal, and 12% had undergone an artificial menopause due to hysterectomy. We have previously screened, by transabdominal ultrasonography, 5479 self-referred asymptomatic women who were recruited by advertisement from the general population [3]. Of these, 45% were premenopausal, 43% were naturally postmenopausal, and 12% had undergone an artificial menopause by the time of the first screening. Clearer pictures were often obtained by transvaginal ultrasonography in the study of cancer families, but identical screen results (i.e., either positive or negative) were recorded by the transabdominal route. Accordingly, the results from the study of women with a history of familial ovarian cancer can be usefully compared with those obtained from the first (or prevalence) screening of the self-referred women from the general population. Thus, 82% of women with a family history of ovarian cancer had a negative screen result compared with 94% of women from the previous study. Conversely, the number of women who had an initial positive result that became negative on rescan was higher (8.2%) than that in the population-based study (2.5%). Up to 4% of naturally postmenopausal women required a rescan showing the initial presence and subsequent regression of an ovarian cyst. Of particular interest is the finding that 9 women with a familial history of ovarian cancer had three to five rescans due to changing morphology and size between the two ovaries and a definitive decision still has to be made whether they should be referred for surgical investigation. Two women have temporarily withdrawn from the study after an initial positive result (one due to depression and the other to agoraphobia). The number of women with an initially positive/finally positive result in the present study was slightly higher at 5.5% compared with 3.6% in the previous study. Forty-three women with a family history of ovarian cancer were referred for surgery, and thirty-nine underwent a laparotomy. Overall 48% of women in the study of familial ovarian cancer had bilateral massescompared with 11% in the previous study. It is also of interest that 15% of abnormal ovaries had more than one type of pathology compared with 3% in the population-based study. After the masseshad been classified, 2.2% of women in the family-based study had a tumor-like condition compared to 0.6% in the population-based study. There was a similar increase in the proportion of women with a benign epithelial tumor, i.e., 2.6% compared to 0.7%. These data suggest that women
with a family history of ovarian cancer are more prone to benign ovarian disease. In accordance with these findings, the false-positive rate of the screening procedure for any ovarian abnormality was 5.2% for the family-based study compared to 3.6% for the self-referred women from the general population. In both studies the highest false-positive rates were observed in women who had undergone an artificial menopause (12.6 and 5.3%, respectively). There was a significant increase (P = 0.04, Fisher’s exact test) in the predictive value of a positive screen result (1 in 13 for the family study and 1 in 99 for the population study). Similarly there was a significant increase (P < 0.02, Fisher’s exact test) in the prevalence of ovarian cancer in the family study (3.9/1000 compared to 0.4/1000). Accordingly, the results to date show that women with a close relative who has developed ovarian cancer have about a lo-fold risk of developing the disease themselves. There is also a higher false-positive rate for ovarian cancer due to the presence of more benign masses, particularly in women who have had a hysterectomy. Most importantly, there is higher predictive value for a positive screening result for primary ovarian cancer and the odds of finding a tumor or tumor-like condition at surgery are relatively high. These calculations show an increased amount of ovarian disease in this study population, and the data are consistent with the hypothesis that some benign tumors may become malignant. The report of a disseminated peritoneal adenocarcinoma (mesothelioma) which produced symptoms 8 months after the last scan raises important questions about the etiology of this disease; in particular, whether some cases of apparent stage III disease may in fact be early cancer developing at several sites simultaneously. The concentration of serum CA-125 was 12 U/ml at the time of the scan and it would be interesting to know whether the disease could have been detected at an early stage by transvaginal ultrasonography with color flow imaging [5]. Notwithstanding these uncertainties we are optimistic about the overall potential value of screening for familial ovarian cancer. Previous workers have been less enthusiastic about screening for the sporadic disease in a clinic population of patients who were also at a higher risk from a variety of factors [19,20]. The possible identification of women at an even higher risk of developing ovarian cancer within our cohort, and the evaluation of second-stage screening procedures, will be reported when more women have been studied. We have also analyzed the family pedigrees of first-degree relatives and calculated their lifetime risks of developing ovarian and other cancers [21]. Although familial ovarian cancer may represent less than 10% of all cases of this disease, the identification of the gene(s) involved might lead to the precise identification of cancer families and also
ULTRASOUND
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women who are at high risk in the general population. Knowledge of the early biochemical events may eventually lead to the development of an immunochemical self-test for early ovarian oncogenesis. The ultimate aim is to develop a logical, comprehensive screening strategy for gynecological cancers. ACKNOWLEDGMENTS This study was undertaken under the auspices of the Imperial Cancer Research Fund (ICRF). The authors are grateful to Sisters Aileen Davies and Taniya Grosvenor-Davies, who took and recorded the family pedigrees, and Mrs. Jill Monk, who typed the manuscript. T.H.B. is supported by the Cancer Research Campaign and M.I.W. by the ICRF, and the Screening Clinic is partially equipped by Aloka Co. Ltd., Tokyo, Japan.
REFERENCES 1. Silverberg, E., Boring, C. C., and Squires, T. S. Cancer statistics, 1990, CA 40, 9-23 (1990). 2. Young, R. C., Walton, L. A., Ellenberg, S. S., Homesley, H. D., Wilbanks, G. D., Decker, D. G., Miller, A., Park, R., and Major, F. Adjuvant therapy in stage I and stage II epithelial ovarian cancer, N. Engl. J. Med. 322, 1021-1027 (1990). 3. Campbell, S., Bhan, V., Royston, P., Whitehead, M. I., and Collins, W. P. Transabdominal ultrasound screening for early ovarian cancer, Br. Med. J. 299, 1363-1367 (1989). 4. Van Nagell, J. R., Higgins, R. V., Donaldson, E. S., Gallion, H. H., Powell, D. E., Paulik, E. J., Woods, C. H., and Thompson, E. A. Transvaginal sonography as a screening method for ovarian cancer. A report on the first 1000 cases screened, Cancer 65, 573577 (1990). 5. Bourne, T H., Campbell, S., Steer, C. V., Whitehead, M. I., and Collins, W. P. Transvaginal color flow imaging: A possible new screening technique for ovarian cancer, Br. Med. J. 299, 1367-1370 (1989). 6. Kurjak, A., Zalud, I., Jurkovic, D., Altirevic, Z., and Miljan, M. Transvaginal color flow Doppler for the assessment of pelvic circulation, Acta Obstet. Gynecol. Stand. 68, 131-135 (1989). 7. Lynch, H. T., Albano, W. A., Lynch, J. F., Lynch, P. M., and Campbell, A. Surveillance and management of patients at high genetic risk for ovarian carcinoma, Obstet. Gynecol. 59, 589-596 (1982).
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8. Piver, M. S., Barlow, J. J., and Sawyer, D. Familial ovarian can-
cer-Increasing in frequency, Obstet. Gynecol. 60, 397-399 (1982). Cramer, D. W., Hutchinson, G. B., Welch, W. R., Scully, R. E., 9. and Ryan, K. J. Determinants of ovarian cancer risk. Reproductive experience and family history, J. Natl. Cancer Inst. 71, 711-716 (1982). 10. Piver, M. S., Mettlin, C. J., Tsukada, Y., Nasca, P., Greenwald, P., and McPhee, M. E. Familial ovarian cancer registry, Obstet. Gynecol. 64, 195-199 (1984). 11. Lynch, H. T., Bewtra, C., and Lynch, J. F. Familial ovarian cancer: Clinical nuances, Am. J. Med. 81, 1073-1076 (1986). 12. Schildkraut, J. M., and Thompson, W. D. Familial ovarian cancer: A population-based case-control study, Am. J. Epidemiol. 128, 456-466 (1988). 13. Ponder, B. A. J., Easton, D. F., and Peto, J. Risk of ovarian cancer associated with a family history: Preliminary report of the OPCS study, in Ovarian cancer: Biological and therapeutic challenges (F. Sharp, W. P. Mason, and R. E. Leake, Eds.), Chapman & Hall Medical, Cambridge, pp. 3-6 (1990). 14. Lynch, H. T., Conway, T., and Lynch, J. Hereditary ovarian cancer, in Ovarian cancer: Biological and therapeutic challenges (F. Sharp, W. P. Mason, and R. E. Leake, Eds.), Chapman & Hall Medical, Cambridge, pp. 7-19 (1990). 15. Campbell, S., Royston, P., Bhan, V., Whitehead, M. I., and Collins, W. P. Novel screening strategies for early ovarian cancer by transabdominal ultrasonography, Br. J. Obstet. Gynaecol. 97, 304311 (1990). 16. Serov, S. F., Scully, R. E., and Sobin, L. H. International histological classification of tumors. No. 9. Histological typing of ovarian tumors, World Health Organization, Geneva (1973). 17. Shepherd, J. H. Revised FIG0 staging for gynaecological cancer, Br. J. Obstet. Gynecol. 96, 889-892 (1989). 18. Bhan, V., Amso, N., Whitehead, M. I., Campbell, S., Royston, P., and Collins, W. P. Characteristics of persistent ovarian masses in asymptomatic women, Br. J. Obstet Gynaecol. 96, 1384-1391 (1989). 19. Granberg, S., and Wikland, M. A comparison between ultrasound and gynecologic examination for detection of enlarged ovaries in a group of women at risk for ovarian carcinoma, J. Ultrasound Med. 7, 59-64 (1988). 20. Andolf, E., Jorgensen, C., and Astedt, B. Ultrasound examination for detection of ovarian carcinoma in risk groups, Obstet. Gynecol. 75, 106-109 (1990). 21 Houlston, R. S., Collins, A., Slack, J., Campbell, S., Collins, W. P., Whitehead, M. I., and Morton, N. E. Genetic epidemiology of ovarian cancer: segregation analysis. Ann. Hum. Genet., in press.
ONCOLOGY
43, 92-97 (1991)
Ultrasound Screening for Familial Ovarian Cancer THOMAS
H. BOURNE, MRCOG, MALCOLM I. WHITEHEAD, FRCOG, STUART CAMPBELL, FRCOG, PATRICK ROYSTON, M.Sc.,* VIJAY BHAN, MRCOG, AND WILLIAM P. COLLINS, D.Sc.
Academic Department of Obstetrics and Gynaecology, Kings College School of Medicine and Dentistry, Denmark Hill, London SE5 8RX, United Kingdom; and *Department of Medical Physics, Royal Postgraduate Medical School, Duane Road, London WI2 ONN, United Kingdom Received February
We have used transvaginal ultrasonography to screen 776 asymptomatic women for familial ovarian cancer. Every woman had at least one first- or second-degreerelative develop the disease (677, 87%; and 98, 13%, respectively). The mean age of the study population was 51 years (range, 24 to 78 years); 52% were premenopausal, 36% were naturally postmenopausal, and 12% had undergone a hysterectomy. Overall, 43 women (5.5%) were referred for surgical investigation and 39 had a laparotomy. Nineteen/thirty-nine (48%) had bilateral ovarian masses,and 15% of abnormal ovaries had more than one type of histopathology. Twenty-three tumors and thirty-two tumor-like conditions were detected. There were 3 casesof primary ovarian cancer (prevalence, 3.9/1000), all FIG0 stage Ia. None of the women has developed ovarian cancer within the first year of the scan (giving a provisional detection rate of 100%). The false positive rate was 40/773 (5.2%), the predictive value of a positive screen result was 7.7%, and the odds in favor of finding any massat laparotomy were about 19 to 1 or for any tumor, 1 to 1. At surgery the odds against fmding primary ovarian cancer were 12 to 1. The positive predictive value of the screening procedure and the prevalence of the disease were signiIicantIy higher than the corresponding values from a previous population-based screening program. 0 1991 Academic
Press, Inc.
INTRODUCTION
28, 1991
Previously we have evaluated the use of transabdominal ultrasonography as the first stage of a screening procedure for ovarian neoplasms in a general population [33. Other workers have reported data on the use of transvaginal ultrasonography for the same purpose [4]. Furthermore, preliminary results have shown that the combined use of transvaginal ultrasonography with color flow mapping and blood flow analyses might be used to distinguish malignant ovarian tumors from many types of benign masses [5,6]. The low incidence of ovarian cancer in the general population means that a multicenter clinical trial is required to evaluate the potential usefulness of these new techniques in a screening procedure for asymptomatic women. An alternative approach is to study women who are at a higher risk of developing the disease. Previous reports of families with several affected relatives, and the results of case-controlled studies and one prospective study, have suggested that a family history of ovarian cancer is an important risk factor for the disease [7-141. Accordingly, we are now studying a cohort of women who have had at least one close relative develop ovarian cancer. This report is concerned with the prevalence of primary cancer and other ovarian masses in the women who have been screened to date, and an evaluation of the first stage of the screening procedure.
Ovarian cancer is an insidious and intractable disease. The incidence in the United States increases with age to about 50 casesper 100,000 women per year (about 20,000 SUBJECTS AND METHODS new cases are reported annually) [l], and the cumulative The aim was to screen about loo0 self-referred, asymprisk up to the age of 75 years is 1.3%. Currently less than 30% of primary cancers are confined to the ovaries at tomatic women (age >25 years) who had had at least one the time of diagnosis (i.e., at FIG0 stage Ia or Ib), and close relative (i.e., a mother, sister, daughter, maternal the overall survival rate is less than 30%. Consequently, or paternal grandmother, or aunt) develop ovarian canthere is a need for an effective procedure to detect early cer. Potential volunteers were made aware of the study ovarian cancer (before metastasis has occurred), when by advertisements placed in the local and national press. the survival rate after surgery alone may be greater than All women who requested further information were sent details about the aims of the study, the screening pro90% [2]. 92 0090-8258191$1.50 Copyright 0 1991 by Academic Press, Inc. All rights of reproduction in any farm reserved.
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cedure, and the action to be taken if an abnormality was detected. The protocol was approved by the Research Ethics Committee of King’s College Hospital. A research nurse constructed a family pedigree from the information provided by each woman. A death certificate or hospital report was required to confirm that the close relative (i.e., the index case) had been diagnosed as having ovarian cancer or had had the disease at the time of death. Volunteers completed a questionnaire designed to provide epidemiological data and a relevant personal medical history. The women were classified as being either premenopausal (a menstrual period within the previous 12 months), naturally postmenopausal (age greater than 35 years and at least 12 elapsed months since the last menstrual period), or artificially postmenopausal (due to hysterectomy but with conservation of at least one ovary). Each screening consisted of one or more ultrasound examinations (scans) by the sequential use of transabdominal and transvaginal probes. The women were instructed to drink a liter of fluid 1 hr before being scanned transabdominally. Both ovaries were located and examined in the transverse and longitudinal planes with a Diasonics SPA 1000 scanner (Diasonics Sonotron, Bedford, UK) using a 3.5-MHz transducer. A morphologically normal ovary gave an image with a smooth ovoid outline and a uniform low-level echogenicity similar to that of the myometrium. Structures resembling normal follicles or corpora lutea in premenopausal women were noted in relation to the first day of the last menses. The maximum transverse (D1), anteroposterior (&), and longitudinal (&) diameters of both ovaries were measured. Ovarian volumes were estimated according to the formula volume = (7r/6 x D, x D2 x D-,). The women were then asked to empty their bladders before being scanned transvaginally in the lithotomy position with a 7.5 MHz transducer [5]. The probe sector angle was 110” and offset 15” to provide a good view of the reproductive organs. The probe was covered with a coupling gel, then a condom, and finally with more gel before insertion into the vagina. The ovaries were located adjacent to the internal iliac vessels, which appeared as anechoic tubular structures with echogenic walls. All observations and measurements were recorded. At each screening the result of a scan was regarded as positive if there was any sign of abnormal ovarian morphology (i.e., areas of hyper- or hypoechogenecity) [3]. Enlarged ovaries with no signs of abnormal morphology were regarded as normal. Women with a normal (negative) result on scanning were contacted 1 year later to check their health and arrange a second screening. Those women with an abnormal (positive) result were rescanned at intervals of 3 to 8 weeks to exclude transient changes in ovarian morphology or size. A volume reduction to less than 68% of that recorded at the initial scan usually
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meant that the eventual screen result was regarded as negative [15]. Exceptions occurred due to adverse morphological changes in the contralateral ovary. If the result of the last scan was still positive the woman was informed about the nature and possible significance of the findings. The information was sent to the appropriate family doctor with a recommendation that the patient be referred to her local specialist or one at King’s College Hospital for further investigations involving laparotomy. Ovarian tissues removed at surgery were sent for histological examination. The stage of the disease was determined by the surgeon and the final diagnosis was based on the report from the histologist. Peripheral blood (10 ml) was taken at each stage of the screening procedure for the retrospective analysis of serum antigens. The ovaries were examined by transvaginal color flow mapping [5] for signs of vascular changes and decreased intratumoral resistance to blood flow at the time of the last scan. These data were also recorded for retrospective analysis. Both of these aspects of the study, and the relative merits of transabdominal and transvaginal ultrasonography, will be reported when sufficient data have been accumulated for statistical analysis. Histopathology
Tissues from abnormal ovaries were examined at the referral hospitals and histology reports were sent to the Ovarian Screening Clinic at King’s College Hospital. The masseswere classified according to criteria recommended by the World Health Organization [16]. The groups were common epithelial tumors, sex cord stromal tumors, germ cell tumors, and tumor-like conditions. The tumors were also classified as benign, borderline, or malignant. The stage of each primary cancer was determined from the surgical records according to the revised recommendations of the International Federation of Gynecologists and Obstetricians [17]. At stage Ia the tumor was limited to one ovary and the capsule was intact. In addition, there was no sign of the tumor on the external surface of the ovary and ascites was not present. Database and Statistical Analysis
A database was established using Foxbase running on an IBM PC/XT-compatible microcomputer with a hard disk. A tape streamer was used for data backup. A suite of programs was developed to facilitate data entry, checking, and retrieval. The detection rate (sensitivity) of the procedure was defined as the proportion of women with primary ovarian cancer who had a positive result on screening. This criterion could only be ascertained within the limitation of the study design, because there is no independent (reference) method to detect early ovarian cancer without resort to surgery. The false-positive rate
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had one ultrasound scan; the remainder (118, 15%) had two to five repeat scans. All abnormal findings were observed by both transabdominal and transvaginal ultrasonography.
TABLE 1 Age and Menopausal State of the Study Population Age (complete years) Menopausal state
-39
Premenopausal 5.5 Naturally postmenopausal 0 Artificially postmenopausal 1 Total
40-49
50-59
60-
249
97
2
403 (52)
17
153
108
278 (36)
28
42
24
95 (12)
All
56 (7) 294 (38) 292 (38) 134 (17) 776 (100)
Note. The values are numbers (percentages) of women.
of the procedure was the proportion of women with a positive result on screening who were apparently free of cancer at the time of surgery (i.e., 100 minus specificity). The positive predictive value was the proportion of women with a positive screening result and ovarian cancer at surgery. The same data were expressed as an odds ratio, which was the chance in favor or against the presence of ovarian cancer at surgery in women with a positive screening result. RESULTS Subjects
The numbers of women (classified by age and menstrual state) are shown in Table 1. A total of 776 women were screened. Their mean age was 51 years (range, 24 to 78 years); 678 (87%) had at least one first-degree affected relative, and 98 (13%) reported a second-degree relative as the index case. Eighteen women (2%) had two firstdegree affected relatives. The mean age of the index cases at the time of death (or diagnosis if still alive) was 64 years (range, 25 to 94 years). Most women (658, 85%)
Outcome of Screening
The numbers of negative, initially positive/finally negative, initially positive/subsequently unknown, and initially positive/finally positive results are shown in Table 2 relative to the menopausal state of the women. Overall 5.5% of women had a positive screening result and were referred for surgical investigation. Higher proportions of premenopausal and artificially postmenopausal women had a positive/negative result than postmenopausal women. Nine women in the initially positive/subsequently unknown group (seven premenopausal, two artificially postmenopausal) are still awaiting a rescan (third to fifth), due to changes in morphology or volume between the two ovaries. Fifteen women are still awaiting a rescan (which has been delayed for personal reasons) and two have temporarily withdrawn from the study. There was a significantly higher proportion of positive/positive results in the group who had undergone an artificial menopause (x2 = 6.39, P = 0.01) than in the other groups. Forty-three women were referred for surgery; four underwent laparoscopy (at which time no ovarian abnormalities were detected), and thirty-nine (87%) underwent laparotomy and bilateral oophorectomy. Characteristics of Masses
A total of 1551 ovaries were screened (776 women), 78 ovaries were examined histologically (39 women), and 55 ovaries were abnormal (37 women). There was a high prevalence of bilateral masses (6/16, 38%) in premenopausal women, 5/12 (429’0) in naturally postmenopausal women, and 7/11 (64%) in artificially postmenopausal
TABLE 2 Results of Screening: Numbers and Percentages of Women in Each Menstrual State Result Negative
Positive/negative”
Positive/unknown
Positive/positive’
Menopausal state
No.
%
No.
%
No.
%
No.
%
Premenopausal Naturally postmenopausal Artificially postmenopausal
319 246
(79.2) (88.5)
46 11
(11.4) (4.0)
19 9
(4.7) (3.2)
19 12
(4.7) (4.3)
71
(74.7)
7
(7.4)
5
(5.3)
12
(12.6)
Total
636
(82.0)
64
(8.2)
33
(4.3)
43
(5.5)
” Result initially positive but abnormality had disappeared at rescan. ’ Patient referred for surgical investigation.
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TABLE 3 Histological Classification of Ovarian Masses Removed at Surgery Menopausal state Premenopausal
Naturally postmenopausal
Artificially postmenopausal
Total (%)
Epithelial Benign Malignant Sex cord, stromal Germ cell Tumor-like
3 2 0 3 14
8 0 0 0 8
5 1 1 0 10
16 (1.0) 3 (0.2) 1 (0.1) 3 (0.2) 32 (2.1)
Total
22
16
17
55 (3.5)
Type
” Of 1551 ovaries screened.
prevalence of primary ovarian cancer was 3/776 (i.e., 3.9 15% of abnormal ovaries. A histological classification, on per 1000) with a 95% confidence interval of 0.8 to II.3 the basis of the principal pathology of the abnormal ova- per thousand. ries removed at surgery, is shown in Table 3. Most per- Follow-up sistent masses were detected in premenopausal women, To date, one interval adenocarcinoma of the peritoand the majority were tumor-like conditions. Three welldifferentiated primary ovarian cancers, all FIG0 stage Ia, neum has been reported. The woman was 55 years old were detected (one serous cystadenocarcinoma, one cyst- and had not menstruated for 4 years. She contacted her adenoma of borderline malignancy, and one endometrioid family doctor about 11 months after the last scan and carcinoma). The women were aged 38, 63, and 54 years, described a 3-month history of abdominal pain and disrespectively; 2 were premenopausal and the other (the tension. Laparoscopy revealed the presence of dissemioldest) had undergone hysterectomy. The first woman had nated nodules in the peritoneum. A CT scan and a repeat a family history of site-specific ovarian cancer; the second ultrasonogram (at the referral hospital) showed that the had a first-degree relative with the disease but the family ovaries were apparently normal. Despite appropriate inpedigree suggested that it was a sporadic version of the vestigations the site of the primary tumor has not been disease. The third woman had a second-degree relative established. (maternal aunt) with ovarian cancer. DISCUSSION women. There was more than one type of pathology in
Evaluation
of Screening Procedure
The screening procedure had an apparent detection rate of 100% (within the limitation of the study design and our knowledge of the disease) with an overall false-positive rate of 5.2% (40/773) based upon the number of women with at least one ovary with a particular morphological abnormality. The false-positive rate for premenopausal women was 16/403 (4.0%), for naturally postmenopausal women 11/278 (4.0%), and for artificially postmenopausal women 19195 (10.6%). This difference is highly significant (x’ = 30.2, P = 0.001). Criteria for assessing the screening procedure are listed in Table 4. The odds in favor of a positive screening result being associated with any ovarian mass (by histological classification) were about 19 to 1, that is, 19 masses per 20 laparotomies. The odds fell to about 1 to 1 for the presence of any ovarian tumor at surgery, that is, 1 tumor per 2 laparotomies. The odds against the detection of primary ovarian cancer (from histological and folloti-up data) were 12 to 1, giving a probability of 1 in 13. The
To our knowledge this is the first report of a prospective study designed to assessthe prevalence of familial ovarian cancer and other pelvic masses,in a group of self-referred TABLE 4 AssessmentCriteria for the Screening Procedure
Ovarian pathology Any mass Any tumor Primary cancer
Detection rate (%> 100
Specificity (%)
Positive predictive value (%I
Odds”
94.8
94.9 51.2 7.7
18.6 to lb 1.0 to 1 12 to 1’
’ Calculated from results of laparotomy. b In favor of positive result on screening indicating the presence of each type of pathology; odds = positive predictive value/(100 - positive predictive value). c Against positive result on screening indicating the presence of each type of pathology; odds = positive predictive value/(100 - positive predictive value).
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women without specific symptoms of the disease. At interview most of the volunteers reported that a first- rather than a second-degree relative had developed ovarian cancer. The relatives most frequently quoted were mother (65%) or sister (25%). Most (87%) of the participants in the study were between 40 and 59 years old; 52% were premenopausal, 36% were naturally postmenopausal, and 12% had undergone an artificial menopause due to hysterectomy. We have previously screened, by transabdominal ultrasonography, 5479 self-referred asymptomatic women who were recruited by advertisement from the general population [3]. Of these, 45% were premenopausal, 43% were naturally postmenopausal, and 12% had undergone an artificial menopause by the time of the first screening. Clearer pictures were often obtained by transvaginal ultrasonography in the study of cancer families, but identical screen results (i.e., either positive or negative) were recorded by the transabdominal route. Accordingly, the results from the study of women with a history of familial ovarian cancer can be usefully compared with those obtained from the first (or prevalence) screening of the self-referred women from the general population. Thus, 82% of women with a family history of ovarian cancer had a negative screen result compared with 94% of women from the previous study. Conversely, the number of women who had an initial positive result that became negative on rescan was higher (8.2%) than that in the population-based study (2.5%). Up to 4% of naturally postmenopausal women required a rescan showing the initial presence and subsequent regression of an ovarian cyst. Of particular interest is the finding that 9 women with a familial history of ovarian cancer had three to five rescans due to changing morphology and size between the two ovaries and a definitive decision still has to be made whether they should be referred for surgical investigation. Two women have temporarily withdrawn from the study after an initial positive result (one due to depression and the other to agoraphobia). The number of women with an initially positive/finally positive result in the present study was slightly higher at 5.5% compared with 3.6% in the previous study. Forty-three women with a family history of ovarian cancer were referred for surgery, and thirty-nine underwent a laparotomy. Overall 48% of women in the study of familial ovarian cancer had bilateral massescompared with 11% in the previous study. It is also of interest that 15% of abnormal ovaries had more than one type of pathology compared with 3% in the population-based study. After the masseshad been classified, 2.2% of women in the family-based study had a tumor-like condition compared to 0.6% in the population-based study. There was a similar increase in the proportion of women with a benign epithelial tumor, i.e., 2.6% compared to 0.7%. These data suggest that women
with a family history of ovarian cancer are more prone to benign ovarian disease. In accordance with these findings, the false-positive rate of the screening procedure for any ovarian abnormality was 5.2% for the family-based study compared to 3.6% for the self-referred women from the general population. In both studies the highest false-positive rates were observed in women who had undergone an artificial menopause (12.6 and 5.3%, respectively). There was a significant increase (P = 0.04, Fisher’s exact test) in the predictive value of a positive screen result (1 in 13 for the family study and 1 in 99 for the population study). Similarly there was a significant increase (P < 0.02, Fisher’s exact test) in the prevalence of ovarian cancer in the family study (3.9/1000 compared to 0.4/1000). Accordingly, the results to date show that women with a close relative who has developed ovarian cancer have about a lo-fold risk of developing the disease themselves. There is also a higher false-positive rate for ovarian cancer due to the presence of more benign masses, particularly in women who have had a hysterectomy. Most importantly, there is higher predictive value for a positive screening result for primary ovarian cancer and the odds of finding a tumor or tumor-like condition at surgery are relatively high. These calculations show an increased amount of ovarian disease in this study population, and the data are consistent with the hypothesis that some benign tumors may become malignant. The report of a disseminated peritoneal adenocarcinoma (mesothelioma) which produced symptoms 8 months after the last scan raises important questions about the etiology of this disease; in particular, whether some cases of apparent stage III disease may in fact be early cancer developing at several sites simultaneously. The concentration of serum CA-125 was 12 U/ml at the time of the scan and it would be interesting to know whether the disease could have been detected at an early stage by transvaginal ultrasonography with color flow imaging [5]. Notwithstanding these uncertainties we are optimistic about the overall potential value of screening for familial ovarian cancer. Previous workers have been less enthusiastic about screening for the sporadic disease in a clinic population of patients who were also at a higher risk from a variety of factors [19,20]. The possible identification of women at an even higher risk of developing ovarian cancer within our cohort, and the evaluation of second-stage screening procedures, will be reported when more women have been studied. We have also analyzed the family pedigrees of first-degree relatives and calculated their lifetime risks of developing ovarian and other cancers [21]. Although familial ovarian cancer may represent less than 10% of all cases of this disease, the identification of the gene(s) involved might lead to the precise identification of cancer families and also
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women who are at high risk in the general population. Knowledge of the early biochemical events may eventually lead to the development of an immunochemical self-test for early ovarian oncogenesis. The ultimate aim is to develop a logical, comprehensive screening strategy for gynecological cancers. ACKNOWLEDGMENTS This study was undertaken under the auspices of the Imperial Cancer Research Fund (ICRF). The authors are grateful to Sisters Aileen Davies and Taniya Grosvenor-Davies, who took and recorded the family pedigrees, and Mrs. Jill Monk, who typed the manuscript. T.H.B. is supported by the Cancer Research Campaign and M.I.W. by the ICRF, and the Screening Clinic is partially equipped by Aloka Co. Ltd., Tokyo, Japan.
REFERENCES 1. Silverberg, E., Boring, C. C., and Squires, T. S. Cancer statistics, 1990, CA 40, 9-23 (1990). 2. Young, R. C., Walton, L. A., Ellenberg, S. S., Homesley, H. D., Wilbanks, G. D., Decker, D. G., Miller, A., Park, R., and Major, F. Adjuvant therapy in stage I and stage II epithelial ovarian cancer, N. Engl. J. Med. 322, 1021-1027 (1990). 3. Campbell, S., Bhan, V., Royston, P., Whitehead, M. I., and Collins, W. P. Transabdominal ultrasound screening for early ovarian cancer, Br. Med. J. 299, 1363-1367 (1989). 4. Van Nagell, J. R., Higgins, R. V., Donaldson, E. S., Gallion, H. H., Powell, D. E., Paulik, E. J., Woods, C. H., and Thompson, E. A. Transvaginal sonography as a screening method for ovarian cancer. A report on the first 1000 cases screened, Cancer 65, 573577 (1990). 5. Bourne, T H., Campbell, S., Steer, C. V., Whitehead, M. I., and Collins, W. P. Transvaginal color flow imaging: A possible new screening technique for ovarian cancer, Br. Med. J. 299, 1367-1370 (1989). 6. Kurjak, A., Zalud, I., Jurkovic, D., Altirevic, Z., and Miljan, M. Transvaginal color flow Doppler for the assessment of pelvic circulation, Acta Obstet. Gynecol. Stand. 68, 131-135 (1989). 7. Lynch, H. T., Albano, W. A., Lynch, J. F., Lynch, P. M., and Campbell, A. Surveillance and management of patients at high genetic risk for ovarian carcinoma, Obstet. Gynecol. 59, 589-596 (1982).
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8. Piver, M. S., Barlow, J. J., and Sawyer, D. Familial ovarian can-
cer-Increasing in frequency, Obstet. Gynecol. 60, 397-399 (1982). Cramer, D. W., Hutchinson, G. B., Welch, W. R., Scully, R. E., 9. and Ryan, K. J. Determinants of ovarian cancer risk. Reproductive experience and family history, J. Natl. Cancer Inst. 71, 711-716 (1982). 10. Piver, M. S., Mettlin, C. J., Tsukada, Y., Nasca, P., Greenwald, P., and McPhee, M. E. Familial ovarian cancer registry, Obstet. Gynecol. 64, 195-199 (1984). 11. Lynch, H. T., Bewtra, C., and Lynch, J. F. Familial ovarian cancer: Clinical nuances, Am. J. Med. 81, 1073-1076 (1986). 12. Schildkraut, J. M., and Thompson, W. D. Familial ovarian cancer: A population-based case-control study, Am. J. Epidemiol. 128, 456-466 (1988). 13. Ponder, B. A. J., Easton, D. F., and Peto, J. Risk of ovarian cancer associated with a family history: Preliminary report of the OPCS study, in Ovarian cancer: Biological and therapeutic challenges (F. Sharp, W. P. Mason, and R. E. Leake, Eds.), Chapman & Hall Medical, Cambridge, pp. 3-6 (1990). 14. Lynch, H. T., Conway, T., and Lynch, J. Hereditary ovarian cancer, in Ovarian cancer: Biological and therapeutic challenges (F. Sharp, W. P. Mason, and R. E. Leake, Eds.), Chapman & Hall Medical, Cambridge, pp. 7-19 (1990). 15. Campbell, S., Royston, P., Bhan, V., Whitehead, M. I., and Collins, W. P. Novel screening strategies for early ovarian cancer by transabdominal ultrasonography, Br. J. Obstet. Gynaecol. 97, 304311 (1990). 16. Serov, S. F., Scully, R. E., and Sobin, L. H. International histological classification of tumors. No. 9. Histological typing of ovarian tumors, World Health Organization, Geneva (1973). 17. Shepherd, J. H. Revised FIG0 staging for gynaecological cancer, Br. J. Obstet. Gynecol. 96, 889-892 (1989). 18. Bhan, V., Amso, N., Whitehead, M. I., Campbell, S., Royston, P., and Collins, W. P. Characteristics of persistent ovarian masses in asymptomatic women, Br. J. Obstet Gynaecol. 96, 1384-1391 (1989). 19. Granberg, S., and Wikland, M. A comparison between ultrasound and gynecologic examination for detection of enlarged ovaries in a group of women at risk for ovarian carcinoma, J. Ultrasound Med. 7, 59-64 (1988). 20. Andolf, E., Jorgensen, C., and Astedt, B. Ultrasound examination for detection of ovarian carcinoma in risk groups, Obstet. Gynecol. 75, 106-109 (1990). 21 Houlston, R. S., Collins, A., Slack, J., Campbell, S., Collins, W. P., Whitehead, M. I., and Morton, N. E. Genetic epidemiology of ovarian cancer: segregation analysis. Ann. Hum. Genet., in press.