- Email: [email protected]
The prevalence of germline BRCA1 and BRCA2 mutations in young women with breast cancer undergoing breast-conservation therapy
The American Journal of Surgery 192 (2006) 58 – 62
Clinical surgery–American
The prevalence of germline BRCA1 and BRCA2 mutations in young women with breast cancer undergoing breast-conservation therapy Mehra Golshan, M.D.a,*, Alex Miron, Ph.D.a, Asa J. Nixon, M.D.b, Judy E. Garber, M.D.c, Ethan P. Cash, B.A.a, James Dirk Iglehart, M.D.a, Jay R. Harris, M.D.b, Julia S. Wong, M.D.b a
Department of Surgery, Brigham and Women’s Hospital, Harvard Medical School, 75 Francis St., Boston, MA 02115, USA b Department of Radiation Oncology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA c Department of Medical Oncology, Dana Farber Cancer Institute, Harvard Medical School, Boston, MA, USA Manuscript received September 14, 2005; revised manuscript December 14, 2005 Presented in part at the 85th annual New England Surgical Society, Montreal, Canada, October 1–3, 2004
Abstract Background: Germline mutations of BRCA1 and BRCA2 increase the risk for breast cancer. Mutation carriers selecting breastconservation therapy (BCT) for treatment of operable breast cancer experience a higher rate of new primary breast cancers. We sought to determine the frequency of BRCA1/BRCA2 mutations in women who underwent BCT. Genetic testing results were compared with the prior probability of mutations in either gene. Methods: Eighty-nine patients age 39 or younger entered the study. Genetic testing was performed for BRCA1 and BRCA2 and the BRCAPRO model determined the probability of carrying a mutation. Results: Eight mutations were discovered (prevalence, 9.0%). Twenty (22%) uncharacterized sequence variants were found. The prior probability of carrying a mutation was 14%. Mutation carriers had a higher prior probability (.49) compared with women with uncharacterized variants (.09) or with normal genes (.11). Conclusions: BRCA1 and BRCA2 mutations are common (9%) among unselected young breast cancer patients undergoing BCT. © 2006 Excerpta Medica Inc. All rights reserved. Keywords: Breast cancer; BRCA1; BRCA2; Prior probability; Breast conservation
Breast-conserving therapy (BCT) has become an accepted treatment option for women with early stage breast cancer based on multiple randomized clinical trials showing equivalent survival compared with mastectomy. BRCA1 and BRCA2 were isolated in 1994 and 1995, respectively. Since then, germline mutations in the breast– ovarian susceptibility genes BRCA1 and BRCA2 have identified women at extremely high risk for developing breast cancer. The lifetime risk for breast cancer for mutation carriers is estimated by several studies to be between 50% and 80% [1–3]. The risk of a second primary breast cancer usually is estimated at about 60% as well. Pretreatment determination of * Corresponding author. Tel.: ⫹1-617-732-8575; fax: ⫹1-617-2646846. E-mail address: [email protected]
BRCA1 or BRCA2 mutations may influence the choice between BCT and mastectomy, and has implications for management of the contralateral unaffected breast. Approximately 7% of all breast cancers are diagnosed in women before age 40 [3]. However, for women carrying the deleterious mutations in BRCA1 or BRCA2, the average age of breast cancer onset is younger by about a decade compared with the average population [4]. Likewise, disease-associated mutations in either gene are more frequent in women with early onset breast cancer. Previous work established that early onset breast cancer often differs with regards to cause, clinical features, and outcome. Some studies suggest that younger patients, and particularly those patients who have BRCA1 and BRCA2 mutations, have higher local recurrence rates and higher contralateral breast cancer occurrence rates compared with older patients [5].
0002-9610/06/$ – see front matter © 2006 Excerpta Medica Inc. All rights reserved. doi:10.1016/j.amjsurg.2005.12.005
M. Golshan et al. / The American Journal of Surgery 192 (2006) 58 – 62
Risks for radiation-induced carcinogenesis, ipsilateral breast recurrence, and a new primary breast cancer in the contralateral breast are increased over the general population [6,7]. The increased likelihood of an inherited mutation in this young population and the higher rates of a second primary breast cancer in patients with an inherited mutation suggest a different set of options for initial surgical treatment. The preoperative knowledge of the presence of a germline mutation may have implications for patient management; specifically, BCT followed by radiation may be less attractive for mutation carriers. The patient with a BRCA1 or BRCA2 mutation may wish to have prophylactic surgery on the contralateral breast, and sequence this procedure in the preoperative surgical management. In this study we measured the prevalence of germline BRCA1 and BRCA2 mutations and compared it with the prior probability of having a germline mutation estimated in a group of women with invasive breast cancer younger than the age of 39 who selected breast conservation.
Methods A study was designed to determine the outcome of conservatively treated young women with BRCA1 or BRCA2 mutations and to compare the outcome with a similar age group of women who did not harbor a deleterious mutation. We identified 265 potentially eligible women diagnosed with early stage breast cancer younger than 39 years of age who received treatment at the Joint Center for Radiation Therapy in Boston between 1987 and 1996. Eighty-nine patients (34%) agreed to participate. Of the remainder, 17% died before being contacted, 24% opted not to participate, 20% were lost to follow-up evaluation, and 5% were not contacted per the request of the physician. After Institutional Review Board approval, the patients provided informed consent to undergo genetic testing used for research and not intended for clinical use. The results were kept confidential and were not provided individually to the participating patients. Individuals in the study population who expressed interest in clinical testing were referred to the Cancer Risk and Prevention Clinics at the DanaFarber Cancer Institute for discussion of risks and benefits of testing. In this study, each patient was assigned a code number along with the blood sample and they were both stripped of patient identifiers to ensure confidentiality. A questionnaire was developed to explore attitudes about genetic testing and its consequences and the questionnaire was pretested before enrollment. Consenting patients completed an interviewer-administered questionnaire. Pedigree information and a blood sample were collected. Lymphocytes were immortalized by Epstein-Barr virus transformation and stored in liquid nitrogen. The prior probability of harboring a clinically relevant mutation in either BRCA1 or BRCA2 was determined by the BRCAPRO statistical model [8]. This model calculates the probability that an individual
59
carries the deleterious BRCA1 or BRCA2 mutation based on personal and family history of breast and ovarian cancer. Once all samples were collected, DNA from 89 patients was extracted and plated at appropriate concentrations for subsequent mutation testing. The strategy to detect alterations in BRCA1 and BRCA2 relied on amplification of exons and adjacent intron sequences using polymerase chain reaction followed by conformation-sensitive gel electrophoresis as described by Korrko et al [9]. A mutation was defined as a biochemically relevant change in the genetic sequence, predicted to cause a loss of function in the altered gene, or a previously reported clinically relevant sequence alteration. Relevant changes usually result in truncation of the protein occurring via a frameshift or nonsense codon. An uncharacterized variant (UV) is usually a missense alteration (an amino acid is exchanged for a different amino acid), although the clinical relevance of this change is unknown. Conservative sequence changes (which do not lead to an amino acid substitution) are not reported. Known mutations and UVs are cited in the Breast Cancer Information Core database at the National Institutes of Health (http://research.nhgri.nih.gov/bic/). Concurrent with the collection phase of the study, patient follow-up data were updated by chart review or by contacting enrolled patients or their physicians to document new contralateral breast cancer, ipsilateral recurrence, distant metastasis, second malignancies, and survival. Statistical considerations Descriptive statistics were used in this sample. The BRCAPRO is a statistical model for calculating an individual’s probability of carrying a mutation of BRCA1, BRCA2, neither, or both on the basis of the individual’s cancer status and the history of breast and ovarian cancer among first- and second-degree relatives. The model uses autosomal-dominant characteristics of the genes, along with prevalence and penetrance, and uses Bayesian updating.
Results Incidence of genetic factors in young women undergoing breast-conservation therapy All of the women in this study had undergone BCT for the local treatment of their cancer. Genetic testing results were grouped into negative (no detectable sequence variation), deleterious mutations, or UVs. Eight mutations were identified, 6 in BRCA1 and BRCA2 in BRCA2, representing a 9% carrier frequency overall for both genes. Twenty (22%) UVs were identified. The sensitivity of conformation-sensitive detection is not established and does not detect large-scale gene deletions. Thus, the frequency reported here may underestimate the true frequency of clinically relevant mutations in this cohort of women. The average
60
M. Golshan et al. / The American Journal of Surgery 192 (2006) 58 – 62
prior probability for the entire group of 89 women, determined by BRCAPRO testing, estimated a 14% rate of mutation. Therefore, the probability of finding a BRCA1 or BRCA2 mutation in young women seeking breast conservation is relatively high. To identify characteristics that identify women at highest risk for carrying mutations, patient and tumor features were studied. Cancer features in the 89 patients The 3 groups (mutation noncarriers, mutation carriers, and UVs) were well matched in terms of T stage with the majority of patients (71–74%) bearing T1 tumors. Most tumors were ductal cancers and contained a mixture of
Fig. 1. Distribution of probabilities of BRCA1 and BRCA2 (mutant), uncharacterized variants, and wild type (no mutation).
Table 1 Patient and tumor characteristics Wild type* N ⫽ 60 Stage I, % Stage II Unknown N (nodal) stage, % 0 1 Clinical size, cm Median, if known Range, if known Pathologic size, cm Median, if known Range, if known Tumor type, % Invasive Invasive and ductal carcinoma in situ Unknown Microscopic margin, % Negative Positive Unknown Chemotherapy, % No Yes Hormone therapy, % No Yes Family history of breast cancer, % First degree relative, % Family history of ovarian cancer, % First degree relative Ashkenazi Jewish lineage (%) Yes First failure site (%) No evidence of disease Local Contralateral Distant * No mutation. † BRCA1 or BRCA2.
Mutation† N⫽8
UV N ⫽ 20
71 27 2
75 25 0
74 16 10
89 11
100 0
94 6
2 .3–4.5
2 1.0–4.0
2 .5–3.5
1.5 .3–4.2
2 1.0–3.0
1.5 .5–3.5
27 57
11 67
20 60
16
22
20
84 13 3
75 25 0
90 5 5
29 71
22 78
40 60
90 10
89 11
95 5
22
67
15
0
33
5
15
11
15
75 13 4 10
77 11 0 0
55 25 5 15
invasive carcinoma and ductal carcinoma in situ (Table 1). The majority of patients had negative margins at the time of surgery. The clinical size of the primary cancer also was similar in the 3 groups, with an average size of about 2 cm at the time of diagnosis. The tumor dimensions by pathologic estimation were not significantly different in the 3 groups, and ranged from 1.5 to 2 cm. Interestingly, none of the 9 mutation carriers had lymph node metastases, compared with 11% of women with normal BRCA1 and BRCA2 genes and 6% of those with UVs. Patient features Clinical-pathologic features of the tumors are shown in Table 1. The median age at diagnosis was 34 to 35 years, and the time from initial diagnosis to interview and testing ranged from 8.2 to 9.1 years. A family history of first-degree relatives with breast cancer or ovarian cancer was seen in 100% of mutation carriers versus less than 22% of the other 2 groups. The percentage of women who were of Ashkenazi Jewish heritage was small (15%) and did not vary among the 3 groups. We used BRCAPRO as an objective way to quantify risk for carrying a BRCA1 or BRCA2 mutation. Fig. 1 shows the distribution of probabilities after BRCA1 and BRCA2 testing, dividing the patients by genotype (no mutations, disease-associated mutations, and UVs). Patients carrying a BRCA1 or BRCA2 alteration had an average prior proba-
Table 2 Prior probability of BRCA1 and BRCA2 by BRCAPRO Testing results
Prior probability, range
Average
Prior probability ⬍10% (%)
No mutation (wild-type) UV Mutation (either gene)
0–.99 .01–.54 .03–.99
.11 .09 .49
53 (83%) 13 (65%) 1 (12.5%)
M. Golshan et al. / The American Journal of Surgery 192 (2006) 58 – 62
bility of carrying a mutation of 49%, which was higher than patients with either no mutation or patients with a UV (Table 2). On average, the estimated risk for carrying a mutation was similar in those women with UVs compared with women with a normal BRCA1 or BRCA2 gene, consistent with the weak or nonexistent association of BRCA1 or BRCA2 UVs with disease (Table 2). After a median of 8.5 years of follow-up evaluation, 11% of the patients with gene mutations, 13% of the group without mutations, and 25% of the women with UVs had a local (ipsilateral) recurrence. With a median of 8.5 years of follow-up evaluation, 11% of patients with gene mutations, 2% of the patients with no mutations, and 5% of the patients with UVs had developed contralateral cancers. Confidence in the data about cancer outcomes is limited by the size of our study; however, patients harboring BRCA1 or BRCA2 mutations do appear to have an increased risk for contralateral breast cancer.
Comments BCT is an accepted option for surgical treatment in appropriately selected women with early stage breast cancer based on 6 large randomized clinical trials showing equivalent survival rates to that of mastectomy [10 –15]. Concern arises when women opting for breast conservation have a genetic mutation in the 2 genes conferring increased cancer risk. We reviewed a group of women who were younger than 39 years of age treated with BCT including radiation therapy. Based on previous work, patients with BRCA1 mutations have a 55% to 85% chance of developing breast cancer and a 15% to 60% chance of developing ovarian cancer, and those with a BRCA2 mutation carry a risk of 37% to 85% of developing breast cancer and a 15% to 27% risk for developing ovarian cancer. We found that 9% of these women harbored a disease-associated allele in BRCA1 or BRCA2, and 22% carried an uncharacterized sequence variant. In the Carolina Breast Study, Newman et al [16] reported an incidence of mutation in unselected women of 3%. A study of patients with BRCA2 mutations looked at women younger than the age of 32 and found a carrier rate of 2.7% [17]. We found a high rate of BRCA mutations in a population only selected by age and by their intent for breast conservation. Previous work on conservatively managed, early onset breast cancer showed varying results in terms of local recurrence. Robson et al [6] reviewed BCT among Ashkenazi women with the BRCA mutation and found a higher rate of local recurrence of 14.9% at 5 years versus 4.5% for those without a mutation, although this did not reach statistical significance. Women in the study by Robson et al [6] also had a higher rate of contralateral breast cancer that did reach statistical significance: 14.8% versus 3.7% at 5 years [6]. In contrast, Pierce et al [18] found that local recurrence did not differ among a group of genetic mutation carriers when
61
compared with a sporadic group. Another study confirming an acceptable rate of local recurrence was from Metcalfe et al [19], who showed a 10-year ipsilateral rate of breast carcinoma of 11.5% in a group of 188 women with a BRCA mutation undergoing BCT. Interestingly, Haffty et al [7] found an extraordinarily high rate of ipsilateral events at 12 years that reached statistical significance: 49% versus 21%. Our study confirmed a higher rate of breast cancer in the contralateral breast, although our sample size was too small to reach statistical significance. When considered alone, our retrospective study also was limited by the fact that patients who had died of disease were not tested. This group may have a higher rate of BRCA1 and BRCA2 mutations. Regardless of the outcomes shown in this small study, mutations in BRCA1 and BRCA2 are relatively common in unselected women undergoing breast conservation. Furthermore, estimates of carrier probability are high in this group. Our findings suggest that women who would develop breast cancer at an early age should be offered genetic counseling. These patients, if identified as carriers, may consider mastectomy on the effected side and contralateral prophylactic mastectomy for the increased incidence of contralateral disease; however, breast conservation is also an appropriate option.
Acknowledgment Supported by the Department of Defense Breast Cancer Research Program, the National Cancer Institute-Harvard Specialized Programs of Research Excellence in Breast Cancer, and the Women’s Cancers Program at the Dana Farber Cancer Institute.
References [1] Hall JM, Lee MK, Newman, et al. Linkage of early-onset familial breast cancer to chromosome 17q21. Science 1990;250:1684 –9. [2] Wooster R, Neuhausen SL, Mangon J, et al. Location of a breast cancer susceptibility gene BRCA 2, to chromosome 13q12-13. Science 1994;265:2088 –90. [3] Easton DF, Ford D, Bishop DT, and the Breast Cancer Linkage Consortium. Breast and ovarian cancer incidence in BRCA 1 mutation carriers. Am J Hum Genet 1995;56:265–71. [4] Gayther SA, Pharoah PD, Ponder BA. The genetics of inherited breast cancer. J Mamm Gland Biol Neoplasia 1997:3;365–76. [5] Seynaeve C, Van Den Bosch LM, Brekelmans CT, et al. Local recurrence following lumpectomy and irradiation in familial and hereditary vs. sporadic breast cancer patients [abstract]. Proc ASCO 1998;17:119a. [6] Robson M, Levin D, Federici M, et al. Breast conservation therapy for invasive breast cancer in Ashkenazi women with BRCA gene founder mutations. J Natl Cancer Inst 2001;91:2112–7. [7] Haffty BG, Harrold E, Khan AJ, et al. Outcome of conservatively managed early-onset breast cancer by BRCA1/2 status. Lancet 2002; 359:1471–7. [8] Berry DA, Parmigiani G, Sanchez J, et al. Probability of carrying a mutation of breast-ovarian cancer gene BRCA 1 based on family history. J Natl Cancer Inst 1997;89:227–38.
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[9] Korkko J, Annunen S, Philajamma T. Conformation sensitive gel electrophoresis for simple and accurate detection of mutations: comparison with denaturing gradient gel electrophoresis and nucleotide sequencing. Proc Natl Acad Sci U S A 1998;95:1681–5. [10] Arriagada R, Le MG, Richard F, et al, for the Institute Gustave Roussy Breast Cancer Group. Conservative treatment versus mastectomy in early breast cancer: patterns of failure with 15 years of follow-up data. J Clin Oncol 1996;14:1558 – 64. [11] Veronesi U, Luini A, Galimberti V, et al. Conservation approaches for the management of stage I/II carcinoma of the breast: Milan Cancer Institute Trials. World J Surg 1994;18:70 –5. [12] Fisher B, Anderson S, Redmond CK, et al. Reanalysis and results after 12 years of follow-up in a randomized clinical trial comparing total mastectomy with lumpectomy with or without irradiation in the treatment of breast cancer. N Eng J Med 1995;333:1456 – 61. [13] Jacobson JA, Danforth DN, Cowan KH, et al. Ten year results of a comparison of conservation with mastectomy in the treatment of stage I and II breast cancer. N Eng J Med 1995;332:907–11.
[14] Van Dongen JA, Bartelink H, Fentiman IS, et al. Randomized clinical trial to assess the value of breast-conserving therapy in stage I and II breast cancer: EORTC 10801 trial. J Natl Cancer Inst 1992;11:15– 8. [15] Bilchert-Toft M, Rose C, Anderson JA, et al. Randomized trial comparing breast conservation with mastectomy: six years of lifetable analysis. J Natl Cancer Inst Monogr 1992;11:19 –25. [16] Newman B, Mu H, Butler LM, et al. Frequency of breast cancer attributable to BRCA 1 in a population-based series of American women. JAMA 1998;289:915–21. [17] Krainer M, Silva-Arrieta S, Fitzgerald MG, et al. Differential contributions of BRCA 1 and BRCA 2 to early onset breast cancer. N Engl J Med 1997;336:1416 –21. [18] Pierce LJ, Strawderman M, Narod SA, et al. Effect of radiotherapy after breast-conserving treatment in women with breast cancer and germline BRCA1/2 mutations. J Clin Oncol 2000;19:3360 –9. [19] Metcalfe K, Lynch HT, Ghadirian P, et al. Contralateral breast cancer in BRCA 1 and BRCA 2 mutation carriers. J Clin Oncol 2004;22: 2328 –35.
Clinical surgery–American
The prevalence of germline BRCA1 and BRCA2 mutations in young women with breast cancer undergoing breast-conservation therapy Mehra Golshan, M.D.a,*, Alex Miron, Ph.D.a, Asa J. Nixon, M.D.b, Judy E. Garber, M.D.c, Ethan P. Cash, B.A.a, James Dirk Iglehart, M.D.a, Jay R. Harris, M.D.b, Julia S. Wong, M.D.b a
Department of Surgery, Brigham and Women’s Hospital, Harvard Medical School, 75 Francis St., Boston, MA 02115, USA b Department of Radiation Oncology, Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, USA c Department of Medical Oncology, Dana Farber Cancer Institute, Harvard Medical School, Boston, MA, USA Manuscript received September 14, 2005; revised manuscript December 14, 2005 Presented in part at the 85th annual New England Surgical Society, Montreal, Canada, October 1–3, 2004
Abstract Background: Germline mutations of BRCA1 and BRCA2 increase the risk for breast cancer. Mutation carriers selecting breastconservation therapy (BCT) for treatment of operable breast cancer experience a higher rate of new primary breast cancers. We sought to determine the frequency of BRCA1/BRCA2 mutations in women who underwent BCT. Genetic testing results were compared with the prior probability of mutations in either gene. Methods: Eighty-nine patients age 39 or younger entered the study. Genetic testing was performed for BRCA1 and BRCA2 and the BRCAPRO model determined the probability of carrying a mutation. Results: Eight mutations were discovered (prevalence, 9.0%). Twenty (22%) uncharacterized sequence variants were found. The prior probability of carrying a mutation was 14%. Mutation carriers had a higher prior probability (.49) compared with women with uncharacterized variants (.09) or with normal genes (.11). Conclusions: BRCA1 and BRCA2 mutations are common (9%) among unselected young breast cancer patients undergoing BCT. © 2006 Excerpta Medica Inc. All rights reserved. Keywords: Breast cancer; BRCA1; BRCA2; Prior probability; Breast conservation
Breast-conserving therapy (BCT) has become an accepted treatment option for women with early stage breast cancer based on multiple randomized clinical trials showing equivalent survival compared with mastectomy. BRCA1 and BRCA2 were isolated in 1994 and 1995, respectively. Since then, germline mutations in the breast– ovarian susceptibility genes BRCA1 and BRCA2 have identified women at extremely high risk for developing breast cancer. The lifetime risk for breast cancer for mutation carriers is estimated by several studies to be between 50% and 80% [1–3]. The risk of a second primary breast cancer usually is estimated at about 60% as well. Pretreatment determination of * Corresponding author. Tel.: ⫹1-617-732-8575; fax: ⫹1-617-2646846. E-mail address: [email protected]
BRCA1 or BRCA2 mutations may influence the choice between BCT and mastectomy, and has implications for management of the contralateral unaffected breast. Approximately 7% of all breast cancers are diagnosed in women before age 40 [3]. However, for women carrying the deleterious mutations in BRCA1 or BRCA2, the average age of breast cancer onset is younger by about a decade compared with the average population [4]. Likewise, disease-associated mutations in either gene are more frequent in women with early onset breast cancer. Previous work established that early onset breast cancer often differs with regards to cause, clinical features, and outcome. Some studies suggest that younger patients, and particularly those patients who have BRCA1 and BRCA2 mutations, have higher local recurrence rates and higher contralateral breast cancer occurrence rates compared with older patients [5].
0002-9610/06/$ – see front matter © 2006 Excerpta Medica Inc. All rights reserved. doi:10.1016/j.amjsurg.2005.12.005
M. Golshan et al. / The American Journal of Surgery 192 (2006) 58 – 62
Risks for radiation-induced carcinogenesis, ipsilateral breast recurrence, and a new primary breast cancer in the contralateral breast are increased over the general population [6,7]. The increased likelihood of an inherited mutation in this young population and the higher rates of a second primary breast cancer in patients with an inherited mutation suggest a different set of options for initial surgical treatment. The preoperative knowledge of the presence of a germline mutation may have implications for patient management; specifically, BCT followed by radiation may be less attractive for mutation carriers. The patient with a BRCA1 or BRCA2 mutation may wish to have prophylactic surgery on the contralateral breast, and sequence this procedure in the preoperative surgical management. In this study we measured the prevalence of germline BRCA1 and BRCA2 mutations and compared it with the prior probability of having a germline mutation estimated in a group of women with invasive breast cancer younger than the age of 39 who selected breast conservation.
Methods A study was designed to determine the outcome of conservatively treated young women with BRCA1 or BRCA2 mutations and to compare the outcome with a similar age group of women who did not harbor a deleterious mutation. We identified 265 potentially eligible women diagnosed with early stage breast cancer younger than 39 years of age who received treatment at the Joint Center for Radiation Therapy in Boston between 1987 and 1996. Eighty-nine patients (34%) agreed to participate. Of the remainder, 17% died before being contacted, 24% opted not to participate, 20% were lost to follow-up evaluation, and 5% were not contacted per the request of the physician. After Institutional Review Board approval, the patients provided informed consent to undergo genetic testing used for research and not intended for clinical use. The results were kept confidential and were not provided individually to the participating patients. Individuals in the study population who expressed interest in clinical testing were referred to the Cancer Risk and Prevention Clinics at the DanaFarber Cancer Institute for discussion of risks and benefits of testing. In this study, each patient was assigned a code number along with the blood sample and they were both stripped of patient identifiers to ensure confidentiality. A questionnaire was developed to explore attitudes about genetic testing and its consequences and the questionnaire was pretested before enrollment. Consenting patients completed an interviewer-administered questionnaire. Pedigree information and a blood sample were collected. Lymphocytes were immortalized by Epstein-Barr virus transformation and stored in liquid nitrogen. The prior probability of harboring a clinically relevant mutation in either BRCA1 or BRCA2 was determined by the BRCAPRO statistical model [8]. This model calculates the probability that an individual
59
carries the deleterious BRCA1 or BRCA2 mutation based on personal and family history of breast and ovarian cancer. Once all samples were collected, DNA from 89 patients was extracted and plated at appropriate concentrations for subsequent mutation testing. The strategy to detect alterations in BRCA1 and BRCA2 relied on amplification of exons and adjacent intron sequences using polymerase chain reaction followed by conformation-sensitive gel electrophoresis as described by Korrko et al [9]. A mutation was defined as a biochemically relevant change in the genetic sequence, predicted to cause a loss of function in the altered gene, or a previously reported clinically relevant sequence alteration. Relevant changes usually result in truncation of the protein occurring via a frameshift or nonsense codon. An uncharacterized variant (UV) is usually a missense alteration (an amino acid is exchanged for a different amino acid), although the clinical relevance of this change is unknown. Conservative sequence changes (which do not lead to an amino acid substitution) are not reported. Known mutations and UVs are cited in the Breast Cancer Information Core database at the National Institutes of Health (http://research.nhgri.nih.gov/bic/). Concurrent with the collection phase of the study, patient follow-up data were updated by chart review or by contacting enrolled patients or their physicians to document new contralateral breast cancer, ipsilateral recurrence, distant metastasis, second malignancies, and survival. Statistical considerations Descriptive statistics were used in this sample. The BRCAPRO is a statistical model for calculating an individual’s probability of carrying a mutation of BRCA1, BRCA2, neither, or both on the basis of the individual’s cancer status and the history of breast and ovarian cancer among first- and second-degree relatives. The model uses autosomal-dominant characteristics of the genes, along with prevalence and penetrance, and uses Bayesian updating.
Results Incidence of genetic factors in young women undergoing breast-conservation therapy All of the women in this study had undergone BCT for the local treatment of their cancer. Genetic testing results were grouped into negative (no detectable sequence variation), deleterious mutations, or UVs. Eight mutations were identified, 6 in BRCA1 and BRCA2 in BRCA2, representing a 9% carrier frequency overall for both genes. Twenty (22%) UVs were identified. The sensitivity of conformation-sensitive detection is not established and does not detect large-scale gene deletions. Thus, the frequency reported here may underestimate the true frequency of clinically relevant mutations in this cohort of women. The average
60
M. Golshan et al. / The American Journal of Surgery 192 (2006) 58 – 62
prior probability for the entire group of 89 women, determined by BRCAPRO testing, estimated a 14% rate of mutation. Therefore, the probability of finding a BRCA1 or BRCA2 mutation in young women seeking breast conservation is relatively high. To identify characteristics that identify women at highest risk for carrying mutations, patient and tumor features were studied. Cancer features in the 89 patients The 3 groups (mutation noncarriers, mutation carriers, and UVs) were well matched in terms of T stage with the majority of patients (71–74%) bearing T1 tumors. Most tumors were ductal cancers and contained a mixture of
Fig. 1. Distribution of probabilities of BRCA1 and BRCA2 (mutant), uncharacterized variants, and wild type (no mutation).
Table 1 Patient and tumor characteristics Wild type* N ⫽ 60 Stage I, % Stage II Unknown N (nodal) stage, % 0 1 Clinical size, cm Median, if known Range, if known Pathologic size, cm Median, if known Range, if known Tumor type, % Invasive Invasive and ductal carcinoma in situ Unknown Microscopic margin, % Negative Positive Unknown Chemotherapy, % No Yes Hormone therapy, % No Yes Family history of breast cancer, % First degree relative, % Family history of ovarian cancer, % First degree relative Ashkenazi Jewish lineage (%) Yes First failure site (%) No evidence of disease Local Contralateral Distant * No mutation. † BRCA1 or BRCA2.
Mutation† N⫽8
UV N ⫽ 20
71 27 2
75 25 0
74 16 10
89 11
100 0
94 6
2 .3–4.5
2 1.0–4.0
2 .5–3.5
1.5 .3–4.2
2 1.0–3.0
1.5 .5–3.5
27 57
11 67
20 60
16
22
20
84 13 3
75 25 0
90 5 5
29 71
22 78
40 60
90 10
89 11
95 5
22
67
15
0
33
5
15
11
15
75 13 4 10
77 11 0 0
55 25 5 15
invasive carcinoma and ductal carcinoma in situ (Table 1). The majority of patients had negative margins at the time of surgery. The clinical size of the primary cancer also was similar in the 3 groups, with an average size of about 2 cm at the time of diagnosis. The tumor dimensions by pathologic estimation were not significantly different in the 3 groups, and ranged from 1.5 to 2 cm. Interestingly, none of the 9 mutation carriers had lymph node metastases, compared with 11% of women with normal BRCA1 and BRCA2 genes and 6% of those with UVs. Patient features Clinical-pathologic features of the tumors are shown in Table 1. The median age at diagnosis was 34 to 35 years, and the time from initial diagnosis to interview and testing ranged from 8.2 to 9.1 years. A family history of first-degree relatives with breast cancer or ovarian cancer was seen in 100% of mutation carriers versus less than 22% of the other 2 groups. The percentage of women who were of Ashkenazi Jewish heritage was small (15%) and did not vary among the 3 groups. We used BRCAPRO as an objective way to quantify risk for carrying a BRCA1 or BRCA2 mutation. Fig. 1 shows the distribution of probabilities after BRCA1 and BRCA2 testing, dividing the patients by genotype (no mutations, disease-associated mutations, and UVs). Patients carrying a BRCA1 or BRCA2 alteration had an average prior proba-
Table 2 Prior probability of BRCA1 and BRCA2 by BRCAPRO Testing results
Prior probability, range
Average
Prior probability ⬍10% (%)
No mutation (wild-type) UV Mutation (either gene)
0–.99 .01–.54 .03–.99
.11 .09 .49
53 (83%) 13 (65%) 1 (12.5%)
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bility of carrying a mutation of 49%, which was higher than patients with either no mutation or patients with a UV (Table 2). On average, the estimated risk for carrying a mutation was similar in those women with UVs compared with women with a normal BRCA1 or BRCA2 gene, consistent with the weak or nonexistent association of BRCA1 or BRCA2 UVs with disease (Table 2). After a median of 8.5 years of follow-up evaluation, 11% of the patients with gene mutations, 13% of the group without mutations, and 25% of the women with UVs had a local (ipsilateral) recurrence. With a median of 8.5 years of follow-up evaluation, 11% of patients with gene mutations, 2% of the patients with no mutations, and 5% of the patients with UVs had developed contralateral cancers. Confidence in the data about cancer outcomes is limited by the size of our study; however, patients harboring BRCA1 or BRCA2 mutations do appear to have an increased risk for contralateral breast cancer.
Comments BCT is an accepted option for surgical treatment in appropriately selected women with early stage breast cancer based on 6 large randomized clinical trials showing equivalent survival rates to that of mastectomy [10 –15]. Concern arises when women opting for breast conservation have a genetic mutation in the 2 genes conferring increased cancer risk. We reviewed a group of women who were younger than 39 years of age treated with BCT including radiation therapy. Based on previous work, patients with BRCA1 mutations have a 55% to 85% chance of developing breast cancer and a 15% to 60% chance of developing ovarian cancer, and those with a BRCA2 mutation carry a risk of 37% to 85% of developing breast cancer and a 15% to 27% risk for developing ovarian cancer. We found that 9% of these women harbored a disease-associated allele in BRCA1 or BRCA2, and 22% carried an uncharacterized sequence variant. In the Carolina Breast Study, Newman et al [16] reported an incidence of mutation in unselected women of 3%. A study of patients with BRCA2 mutations looked at women younger than the age of 32 and found a carrier rate of 2.7% [17]. We found a high rate of BRCA mutations in a population only selected by age and by their intent for breast conservation. Previous work on conservatively managed, early onset breast cancer showed varying results in terms of local recurrence. Robson et al [6] reviewed BCT among Ashkenazi women with the BRCA mutation and found a higher rate of local recurrence of 14.9% at 5 years versus 4.5% for those without a mutation, although this did not reach statistical significance. Women in the study by Robson et al [6] also had a higher rate of contralateral breast cancer that did reach statistical significance: 14.8% versus 3.7% at 5 years [6]. In contrast, Pierce et al [18] found that local recurrence did not differ among a group of genetic mutation carriers when
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compared with a sporadic group. Another study confirming an acceptable rate of local recurrence was from Metcalfe et al [19], who showed a 10-year ipsilateral rate of breast carcinoma of 11.5% in a group of 188 women with a BRCA mutation undergoing BCT. Interestingly, Haffty et al [7] found an extraordinarily high rate of ipsilateral events at 12 years that reached statistical significance: 49% versus 21%. Our study confirmed a higher rate of breast cancer in the contralateral breast, although our sample size was too small to reach statistical significance. When considered alone, our retrospective study also was limited by the fact that patients who had died of disease were not tested. This group may have a higher rate of BRCA1 and BRCA2 mutations. Regardless of the outcomes shown in this small study, mutations in BRCA1 and BRCA2 are relatively common in unselected women undergoing breast conservation. Furthermore, estimates of carrier probability are high in this group. Our findings suggest that women who would develop breast cancer at an early age should be offered genetic counseling. These patients, if identified as carriers, may consider mastectomy on the effected side and contralateral prophylactic mastectomy for the increased incidence of contralateral disease; however, breast conservation is also an appropriate option.
Acknowledgment Supported by the Department of Defense Breast Cancer Research Program, the National Cancer Institute-Harvard Specialized Programs of Research Excellence in Breast Cancer, and the Women’s Cancers Program at the Dana Farber Cancer Institute.
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