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Cancers of the salivary gland: Workplace risks among women and men
ELSEVlER
Cancers of the Salivary Gland: Workplace Risks Among Women and Men G. MARIE SWANSON,
PHD,
AND PATRICIA
BRISSETTE BURNS, MPH
PURPOSE: The purpose of this study was to assessthe risk of salivary gland cancers associated W& diverse occupations and indrtstries. MJZHODS: A populationbased case referent study utilized data obtained from a SEER program cancer registry for cases and by telephone interview for cases and referents to evaluate workplace risk> of salivary gland cancer for black and white women and men. RESULTS: Significantly elevated odds ratios were observed among women empIoyed as hairdressers and those working in beauty shops. CONCLUSIONS: The risk of salivary gland cancer is elevated among women employed as hairdresseri. Further research should assessdyes, sprays, and other inhaled chemicals that may be acting as carrinoeens Ann Epidemiol 1997;7:369-374. 0 1997 Elscvier Science Inc. KEY WORDS:
Salivary Gland Neoplasms, Race, Gender, Hairdresser, Occupation,
INTRODUCTION The etiology of salivary gland cancers is poorly defined, in part, because these malignant tumors are quite rare. The incidence rate per 100,000 population for salivary gland cancers in the United States (based on Surveillance, Epidemiology, and End Results Program (SEER) data, 19871991) is 0.9, and mortality is 0.2 per 100,000 (1). Rates of incidence and mortality of cancers of the salivary gland vary by race and gender. The average annual ageadjusted incidences per 100,000 are 1.2 for white males, 1.0 for black males, and 0.7 for white females and for black females. The average annual age-adjusted mortality per 100,000 population for this rare cancer is 0.3 for white males and black males, while for white females and for black females the mortality rates are 0.1 and 0.2, respectively. Salivary gland cancers occur at younger ages among women than among men. The median age at diagnosis for women is 61 for whites and 62 for blacks. Among both black and white men, the median age at diagnosis is 65 ( 1). Although overall 5-year survival is good (72.8%), it is substantially higher for women (8 1.4%) than for men (64.9%) (I). Survival differences between blacks and whites diagnosed with salivary gland cancers are greater among women than men. The 5-year relative survival among white females is 81.0% as compared with 72.8% among black women. For
From the Cancer Center, Michtgan Sate University, East Lansing, MI. Address reprint requesrsto: Dr. (3. Marie Swanson, Michigan State University, Cancer Center, A-128 East Fee Hall, East Lansing, MI 48824-1316. Received July 17, 1996; accepted May 1, 1997. 8 1997 Eisevier Science Inc. All rights reserved. 655 Avenue of the Americas. New York. NY 10010
Case-r&rent
St+&
men, the li-year reiative survival is higher among black men (68.8%) than among white men (64.3%) ( I ). Early studies of salivary gland cancers were primarily descriptive, focusing upon age, race, ethnicity, and specific anatomic site and histology (2-6). These studies observed that nearly all cancers of the salivary glands occurred in the parotid gland (2, 3). Excess risk of salivary gland cancers has been found among natives of Alaska and Cireenland; this observation may be explained by exposure to EpsceinBarr virus, which is common among the Inuit in these areas (4, 5). Another early study suggested that salivary gland cancers may be related to abnormal hormonal status, since high rates of breast cancer occur in these patients both before and after their diagnosis of salivary gland cancers (6). Although the number of published studies investigating salivary gland cancers is small, two risk factors have emerged: radiation exposure (‘7-l 7) and a previous diagnosis of cancer ( 15, 17-19). A few studies have shown some association between occupation and salivary gland cancers ( I?, 20,2 1).
METHODS This case-referent study includes salivary gland cancer cases and a population comparison group from the Occupational Cancer Incidence Surveillance Study (CCISS) (22), a population-based investigation of occupational risk factors for cancers diagnosed among residents of the tri-county Detroit area. Cancer cases were identified through the Metropolitan Detroit Cancer Surveillance System, a participant in the SEER program. A rapid reporting system was utilized to enroll cancer case subjects within 2-6 weeks after diagnosis. Incident salivary gland cancer cases in this study were diagnosed between November 1984 and Match 1991. Subjects
370
AEP Vol. 7, No. 6 AugUst 1997: 369-374
Swanson and Burns SALIVARY GLAND CANCER IN THE WORKPLACE
Selected
Abbreviationsand Acronyms
SEER = Surveillance, Epidemiology, and End Results Program OCISS = Occupational Cancer Incidence Surveillance Study OR = odds ratio CI = confidence interval
in the population comparison group were selected by random-digit dialing (23). Occupations categorized as unexposed for this study included such groups as housewives, administrators, teachers, and clerical workers. Examples of industries categorized as unexposed are real estate, schools, banks, and department stores. A more detailed description of the OCISS is found in an earlier report (22). This study includes black and white men and women in the group aged 40-84 years: 163 persons with salivary gland cancers and 375 1 population referents. Subjects or their surrogates (spouse or other first+degree relative of the subject) were interviewed by telephone. The interview obtained info~ation on lifetime occupational history, lifetime smoking history, adult medical history, residential history, education, birthplace, and other demographic variables. The response rates for casesand the comparison group were 94% and 97%, respectively. Occupation and industry data obtained by the telephone interview were coded according to the 1980 U.S. Census Bureau classification codes (24). Grouped codes were created by combining codes for specific occupations or induse tries characterized by similarities in work exposures. Before analysis, an unexposed group was defined by selection of occupations and industries with little or no exposure to carcinogens (22). All other occupations and industries were considered exposed to some form of potentially carcinogenic substance for the analysis, Work histories were evaluated on the basis of a subject reporting ever having been employed in a particular occupation or industry. Maximum likelihood estimates of the odds ratio (ORs) for ever smoking and for occupations and industries were obtained from multiple logistic regression analyses (25). The risk of occurrence of salivary gland cancers by smoking status was estimated by comparison of smokers with nonsmokers. The potential confounding effects of age at diagnosis, gender, and race were controlled for in the analysis. The risk of occurrence of salivary gland cancers among exposed occupations and industries was estimated in comparison to this risk among subjects who were employed solely in unexposed occupations and industries during their lifetime. Analyses were performed separately for men and women. The potential confounding effects of age, cigarette smoking, and race were controlled for in the model. The ORs and their respective confidence intervals were calculated for each occupa+ tion and industry category that included at least five cases.
RESULTS Table 1 includes the distribution of Occupational Cancer Incidence Surveillance System salivary gland cancers by anatomic site and histologic type. The predominant anatomic site for salivary gland cancers was the parotid gland, while the most common cell type was mucoepidermoid carcinoma. There is little difference between men and women in the specific anatomic site; however, there are differences in the histologic type, with women having a greater proportion characterized as acinar cell adenomas, whiie men have a greater proportion identified as squamous cell carcinoma or adenocarcinoma. Table 2 presents the distribution of salivary gland cancers and population referents by demographic and smoking characteristics. Women and men diagnosed with cancers of the salivary gland were younger than the population comparison group and included a higher proportion of whites. Most interviews were conducted with subjects directly for both cases (77.3%) and contrdls (92.0%). Among cases, interviews were conducted with next-of-kin proxies for 14.1% of participants who were alive but too ill to respond by interview and for 8.6% who were deceased at time of interview. Among controls, 7.9% of interviews were conducted with proxies when controls were alive but too ill for interview, and less than 1% were conducted among proxies for deceased controls. Comparison of cigarette smoking status between persons diagnosed with salivary gland cancers and the population referents revealed a significant elevated OR among persons with 80 pack-years or more of cigarette smoking (Table 3). Table 4 presents the risk of occurrence of salivary gland cancers by occupation. A statistically significant elevated odds ratio is observed among women ever employed as hairdressers (OR, 2.7; 95% confidence interval (CI), 1.1-6.5). The mean number of months of employment as a hairdresser was 97.7. Two women were employed for > 15 years as hairdressers, one for 6 years, and four for 6 2 years. Only two of these women had ever smoked cigarettes. Other occupations with ORs of > 2.0 include women ever employed as stock clerks (OR, 2.8; 95% CI = 1.0-8.0) and men ever employed as machine repairers (OR, 3.6; 95% CI = 0.7, 18.9). Table 5 describes the risk of salivary gland cancer by industry. The OR is statistically significantly elevated among women ever employed in beauty shops (OR, 3.4; 95% CI = 1.4-7.9). Other industries for which the OR is > 2.0 include men ever employed in the railroad industry (OR, 5.3; 95% CI, 0.5-55.6), oil and gassales (OR, 3.8; 95% CI, 0+4-32.8), and the post office (OR, 3,l; 95% CI, 0.3-30.0).
DISCUSSION A clear observation in this study is the association between employment in hairdressing and the occurrence of cancers
TABLE 1. Distribution of cancersof the salivary gland included in OCISS by gender, anatomic site, and histologic type --.__ Male Cancer
Female
NO.
%
No.
Site Parotid S&man&h&x Suhhngual Major salivary glands, NOS Tt ml
64 15 3 2
76.2 17.9 3.6 2.4
hi 13 4
Histc&>gtc Type Mucoe~~dermoid carcinoma Squamous cell carcinoma Ailmwxcmoma Acinar cell adenuma Adenoid cystic carcinoma Orhcr Tml
16 18 18 7 6 19
19.0 21.4 21.4 8.3 21.7 22.6
TABLE 2. Distribution of salivary gland cancer casesand population referents by race, age,gender, smoking status, and pack-yearsof smoking Population referents
Salivary gland cancer cases Group
NO.
5%
NO.
%
Race White Black U&et
141 19 3
86.5 11.7 1.8
2955 795 1
78.8 21.2 0.0
-I-mr i
163
100.0
3751
100.0
Age 40-49 50-59 6049 m-79 PO-84 Unknown
16 32 56 47 8 4
9.8 19.6 34.4 28.8 4.9 2.5
275 697 1336 1108 332 3
7.3 18.6 35.6 29.5 8.9 0.1
TCK:Il
163
100.0
3751
100.0
Getlifer Male Fetnale
84 79
il.5 48.5
1807 1944
48.2 51.8
Torai
163
100.0
3751
100.0
96 67
58.9 41.1
2131 1620
56.8 43.2
Total
163
--.-. NC’ --’
77.2 lb.5 5.1 I.3
76.7 17.2
4.3 I.8 I:@.0
]I’,’
of the salivary gland. This finding was apparent whether the analysis was performed for the occupational category of hairdressing or the industry category of beauty shop. This association represents a new observation, since previous studies concerned with cancer risks among hairdressers have not included any cases of salivary gland cancers (26, 27). A related study, not focused upon occupational exposure,
Smoking status Ever smoked Never smoked
P’(Tdl 041
100.0
3751
100.0
19 8 8 15 1C t9
1’4.0 10.1 10.1 19.1 12.7 24.0
did observe an association between the ~.tseof hair dyes and cancers of the saGvary gland (16). Beauticians are exposed to various chemicals, including hair sprztvs and permanent and wave solutions. Women employed as stock clerks alst: had an elevated odds ratio. Exposures in this occupatior? are likely to be diverse and require more thorough assessment. Potential leads concerning the occu~~~ri~~naletiology of salivary gland cancers among men include the occupation of machine repairer as well as jobs in the railroad, gas and oil sales,and post office industries. Each of these work situations involve potential exposure to motor exhaust. With the exception of post of&e workers, people in these occupations aiso are likely to have some exposure to qc?lvents and cutting oils. A common thread in all of the occuparlrms and industries among which this study observed elevated risk of cancers of the salivary gland is exposure to inhale’3 chemicals, fumes, and sprays. This route of exposure is the: most plausible for the anatomic sites encompassed in rhe catt:g
TABLE 3. Risk of salivary gland czmcerby Ix+&-yearsof cigarette smoking --..No.
of
Smokmg status1
CZWS
Referents
Non-smoker < 20 pack years Z&39 pack years 40-59 pack years 60-79 pack years
67 23 21 22 6
IhZC 656 5% 436 188
3 80 pack years
18
225
95% i ‘U,.iz Confidence f!~lrM, Interval .~ 6 eferent Cin~p 5’3 O-i-1.4 .,’ t ’ 0.6-1.5 !.I O.?-?.<) \“iI. O.2- I.6 i.h
1.0-1.3
*There were four cases and 39 referentc frlr whanl numhcr ,\1’pack-year* was unknown.
372
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Swanson and Bums SALIVARY GLAND CANCER IN THE WORKPLACE
TABLE 4.
Risk of salivary
gland cancer by occupation No. of
Occupation, exposure
Cases
Referents
Men” Agricultural worker Laborer Assembler Janitor Mechanic Machine repair Tool and die worker Metal finisher Machine operator Driver Military Unexposed
10 10 18 6 13 7 7 7 8 9 52 3
186 312 404 146 147 83 193 260 153 209 1054 58
Women” Stock clerk Assembler Quality control checkers Private household service Hairdressers Health technicians Foodworkers Unexposed
5 10 5 9 7 7 5 34
35 154 90 210 56 138 181 809
Odds ratio
95% Confidence interval
1.1 0.8 0.9
0.2-4.2 0.2 3.2 0.2-3.2 0.3-7.9 0.5-7.7 0.7-18.9 0.2-3.4 0.2-2.4 0.3-4.8 0.2-3.3 0.3-2.9
2.8 1.6 1.4 0.7 2.7 1.0 0.5
1.0-8.0 0.8-3.4 0.5-3.9 0.3-1.7 1.1-6.5 0.4-2.4 0.2-1.3
1.0 0.8 0.9 1.6 1.9 3.6 0.8
0.5
a Blacks and whites combined.
glands because they are all located in the area of the head and neck. Previous studies have suggestedthat workplace exposures may increase the risk of salivary gland cancers. Some of
salivary
TABLE 5.
Risk of salivary
these studies have focused upon occupational exposure to radiation, including exposure of fluorospar miners to radon progeny and employment at the Lawrence Livermore National Laboratory (28, 29). There is also a suggestion of a
gland cancer by industry No. of
Industry exposure
Odds ratio
95% Confidence interval
Cases
Referents
Men” Farming Construction Automobile manufacturing Railroad Post office Food store Oil and gas sales Military Unexposed
10 9 40 5 5 5 8 52 2
184 293 971 33 78 114 73 1063 36
1.6 1.9 1.7 5.3 3.1 1.4 3.8 1.8
0.2-13.8 0.2-16.6 0.2-12.7 0.5-55.6 0.3-30.0 0.2 14.0 0.4-32.8 0.2-13.5
Women” Automobile manufacturing Private household Laundry/dry cleaning Beauty shop Medical office Hospital Unexposed
19 9 5 8 5 7 24
341 226 85 61 76 231 605
1.6 0.8 1.4 3.4 1.7 0.8
0.3-3.0 0.3-1.9 0.5-3.8 1.4-7.9 0.6-4.7 0.3-1.9
a Blacks and whites combined
AEP b’& 7, NIX 6 Auffltsr 1997: 369-374
relationship between salivary gland cancers and asbestos mining (30) and employment in rubber products manufacturing plants (2 1f . High rates of salivary gland cancers have been found among workers in livestock-feed processing companies in Denmark (3f), among workers employed in a mustard-gas manufacturing plant in England during Worfd War II (32) , and among underground colliery workers in Australia (33). A study in several automobile plants in the Detroit metropolitan area found an increase in salivary gland cancer among woadworkers (20). Two salivary gland cancers were observed among automotive woodworkers when fewer than one case was expected. An increase in salivary gland cancers among woodworkers was not observed in our study. In an analysis not shown, cancer risks in occupations within the auromobile industry were assessed,and no increase in risk was observed among woodworkers in the automobile industry. In contrast to previous observations, this study found an association between cigarette smoking and the occurrence of cancers of the safivary gland. This association was observed only among those with the highest level of exposure to cigarette smoking: 3 80 pack-years. Therefore, it will be important for future studies of the etiology of salivary gland cancers to evaluate this relationship further. The resuks of the study are limited by the lack of information on specific exposures in the workpiace and outside of work. OCISS was designed to evaluate occupationa risks for eleven cancer sites, encompassing => 20,000 subjects. Therefore, obtaining information about specific exposures for an individual cancer sire was not practical. Although a larger proportion of case than control interviews were conducted among proxies, the information provided regarding occupational history and cigarette smoking is simifar in completeness and detail to that provided by subjects themselves. This would suggest that the next-of-kin respondents can provide such information. Although we assume that such ~~~f~~rrnat~on is accurate, we have no secondary source of data against which to validate these responses. The limitations of the data are offset by the many strengths of the study. These include the detailed occupation and smoking hisrories ubtained, the use of population-based cases and controls, and the high response rate. Much of the research regarding salivary gtand cancers has focused on radiation exposure (7-17). Atomic bomb survivors (9, 10) and patients exposed to radiation for medical conditions or diagnosric purposes (7, 8, 1l-13, 15-17) have consistently shown an increased risk of salivary gland cancers and other head and neck cancers. Radiation therapy for chitdhood diseases,such as ringworm, which were treated by irradiation of the head and neck area, is implicated in the etiology of salivary gland cancers (8,11,34). In addition, adults who underwent radiation therapy to the head and neck, face, or upper torso, often for conditions such as acne,
eczema, and hair removal, have been observed to experience excess rates of salivary gland cancers (3, 7, /3, 16, 17). Exposure to diagnostic radiation for medical and dental assessments has been implicated in the etiology of these cancers as welt (15 1.The present study could not addressthis issue because such exposure information was not collected during the interviews. Several studies have found that patients previously diagnosed with skin cancers have high rates s>fsubsequent cancers of the salivary gland (35,361. It is hy~thes~~ed that this association may result from exposure to ultraviolet radiation (14, 36). In the present study, no association was observed between employment in which radiation exposure was likely to have occurred and the occurrence of salivary gland cancers. The increased risk of salivary gland cancer among women employed in beauty shops is intriguing. Further investigation should identify the specific exposures involved, which may include permanent and wave-setting solutions, hair dyes, or hair sprays. The results of this study &o strorrgiy suggest that the understanding of the etiology of cancers of the salivary gland may be enhanced by focusing upon inhaled exposures (e.g.* motor exhaust, fumes, and sprays). Our observations suggesttwo directions for future research: (i) analysis of specific exposures experienced Fy hairdressers while they are engaged in this work activity, pe&aps in a ‘largercase referent study; and (ii) assessmenri:i rhe role c,Etobacco use by gender, age, histologic type, ant1 ~~ccl~pation in a larger case-referent study. -----REFERENCES 1.
2. 3.
4.
5. 6. 7. 8. 9.
10.
314
Swanson and Bums SALIVARY GLAND CANCER IN THE WORKPLACE
bomb survivors, Hiroshima, Japan. I. Epidemiologic observations. Cancer. 1976;38:2464-2468. 11. Schneider AB, Favus MJ, Stachura ME, Arnold MJ, Frohman LA. Salivary gland neoplasms as a late consequence of head and neck irradiation. Ann Int Med. 1977;87:1~144. 12. Maxon HR, Saenger EL, Thomas SR, et al. Radiation-associated carcinoma of the salivary gland: A controlled study. Ann Otolaryngol. 1981;90:107-108. 13. Palmer JA, Mustard RA, Simpson WJ. Irradiation as an etiologic factor in tumors of the thyroid, parathyroid, and salivary glands. Can J Surg. 1980;23:39-42. 14. Spits MR, Sider JG, Newell GR, Batsakis JG. Incidence of salivary gland cancer in the United States relative to ultra-violet radiation exposure. Head Neck Surg. 1988;10:305-308. 15. PrestonMartin S, Thomas DC, White SC, Cohen D. Prior exposure to medical and dental X-rays related to tumors of the parotid gland. JNCI. 1988;80:943-949. 16. Spitz MR, Fueger JJ, Goepfert J, Newell GR. Salivary gland cancer. A case-control investigation of risk factors. Arch Otolaryngol Head Neck Surg. 1990;116:1163-1166. 17. Spitz MR, Tilley BC, Batsakis JG, Gibeau JM, Newell GR. Risk factors for major salivary gland carcinoma. A case-comparison study. Cancer. 1984;54:1854-1859. 18. Horn-Ross PL, West DW, Brown SR. Recent trends in the incidence of salivary gland cancer. Int J Epidemiol. 1991;20:628-633. 19. Spitz MR, Newell GR, Gibeau JM, et at. Multiple primary cancer risk in patients with major salivary gland carcinoma. Ann Otol Rhino1 Laryngol. 1985;94:129-132. 20. Swanson GM, Belle SH. Cancer morbidity among woodworkers in the U.S. automotive industry. J Occup Med. 1982;24:315-319.
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industry in the Detroit metropolitan area. Am J Ind Med. 1991;19: 655-671. 23. Waksberg J. Sampling methods for random digit dialing. J Am Stat Assoc. 1978;73:40-46. 24. U.S. Department of Commerce, Bureau of the Census. 1980 Census of Population: Classified Index of industries and Occupations. finat ed. Washington, DC: U.S. Government Printing Gffice; 1982. 25. Breslow NE, Day NE. Statistical methods in cancer research. Vol. 1. The analysis of case-control studies. Lyons, France: International Association for Cancer Research; 1980;192-246. 26. Teta MJ, Wairath J, Meigs JW, Flannery JT. Cancer incidence among cosmetologists. JNCI. 19~72:1051-1057. 27. Kono S, Tokudome S, lkeda M, Yoshimura T, Kuratsume M. Cancer and other causes of death among female beauticians. JNCI. 1983; 1) 70:443446. 28. Morrison HI, Semenciw RM, Mao Y, Wigle DT. Cancer mortality among a group fluorspar miners exposed to radon progeny. Am J Epidemiol. 1988;128:126&1275. 29. Reynolds I’, Austin DF. Cancer incidence among employees of the Lawrence Livermore National Laboratory, 1969-1980. West J Med. 1985;142:214-218. 30. Graham S, Blanchet M, Rohrer T. Cancer in asbestos-mining and other areas of Quebec. J Nat1 Cancer Inst. 1977;59:1139-1145. 31. Olsen JH, Dragsted L, Autrup H. Cancer risk and occupational exposure to aflatoxins in Denmark. Br J Cancer. 1988;58:392-396. 32. Easton DF, Peto J, Dolt R. Cancers of the respiratory tract in mustard gas workers. Br J Indus Med. 1988;45:652-659. 33. Corbett S, O’Neill BJ. A cluster of cases of lymphoma in an underground colliery. Med J Aust. 1988;149:178-185. 34. Maxon HR, Saenger EL, Thomas SR, et al. Radiation-associated catcinoma of the salivary glands-A controlled study. Ann Otol. 1981; 90:107-108.
21. Mancuso TF, Brennan MJ. Epidemiologi~l considerations of cancer of the gallbladder, bile ducts and salivary glands in the rubber industry. J Occup Med. 1970;12:333-341.
35. Teppo L, Pukkaia E, Saxen E. Multiple cancer-An exercise in Finland. JNCI. 1985;75:207-217.
22. Bums PB, Swanson GM. The Occupational Cancer Incidence Surveillance Study (GCISS): Risk of lung cancer by usual occupation and
36. Spitz MR, Sider JG, Newell OR. Salivary gland cancer and risk of subsequent skin cancer. Head Neck. 1990;12:254-256.
epidemiologicat
Cancers of the Salivary Gland: Workplace Risks Among Women and Men G. MARIE SWANSON,
PHD,
AND PATRICIA
BRISSETTE BURNS, MPH
PURPOSE: The purpose of this study was to assessthe risk of salivary gland cancers associated W& diverse occupations and indrtstries. MJZHODS: A populationbased case referent study utilized data obtained from a SEER program cancer registry for cases and by telephone interview for cases and referents to evaluate workplace risk> of salivary gland cancer for black and white women and men. RESULTS: Significantly elevated odds ratios were observed among women empIoyed as hairdressers and those working in beauty shops. CONCLUSIONS: The risk of salivary gland cancer is elevated among women employed as hairdresseri. Further research should assessdyes, sprays, and other inhaled chemicals that may be acting as carrinoeens Ann Epidemiol 1997;7:369-374. 0 1997 Elscvier Science Inc. KEY WORDS:
Salivary Gland Neoplasms, Race, Gender, Hairdresser, Occupation,
INTRODUCTION The etiology of salivary gland cancers is poorly defined, in part, because these malignant tumors are quite rare. The incidence rate per 100,000 population for salivary gland cancers in the United States (based on Surveillance, Epidemiology, and End Results Program (SEER) data, 19871991) is 0.9, and mortality is 0.2 per 100,000 (1). Rates of incidence and mortality of cancers of the salivary gland vary by race and gender. The average annual ageadjusted incidences per 100,000 are 1.2 for white males, 1.0 for black males, and 0.7 for white females and for black females. The average annual age-adjusted mortality per 100,000 population for this rare cancer is 0.3 for white males and black males, while for white females and for black females the mortality rates are 0.1 and 0.2, respectively. Salivary gland cancers occur at younger ages among women than among men. The median age at diagnosis for women is 61 for whites and 62 for blacks. Among both black and white men, the median age at diagnosis is 65 ( 1). Although overall 5-year survival is good (72.8%), it is substantially higher for women (8 1.4%) than for men (64.9%) (I). Survival differences between blacks and whites diagnosed with salivary gland cancers are greater among women than men. The 5-year relative survival among white females is 81.0% as compared with 72.8% among black women. For
From the Cancer Center, Michtgan Sate University, East Lansing, MI. Address reprint requesrsto: Dr. (3. Marie Swanson, Michigan State University, Cancer Center, A-128 East Fee Hall, East Lansing, MI 48824-1316. Received July 17, 1996; accepted May 1, 1997. 8 1997 Eisevier Science Inc. All rights reserved. 655 Avenue of the Americas. New York. NY 10010
Case-r&rent
St+&
men, the li-year reiative survival is higher among black men (68.8%) than among white men (64.3%) ( I ). Early studies of salivary gland cancers were primarily descriptive, focusing upon age, race, ethnicity, and specific anatomic site and histology (2-6). These studies observed that nearly all cancers of the salivary glands occurred in the parotid gland (2, 3). Excess risk of salivary gland cancers has been found among natives of Alaska and Cireenland; this observation may be explained by exposure to EpsceinBarr virus, which is common among the Inuit in these areas (4, 5). Another early study suggested that salivary gland cancers may be related to abnormal hormonal status, since high rates of breast cancer occur in these patients both before and after their diagnosis of salivary gland cancers (6). Although the number of published studies investigating salivary gland cancers is small, two risk factors have emerged: radiation exposure (‘7-l 7) and a previous diagnosis of cancer ( 15, 17-19). A few studies have shown some association between occupation and salivary gland cancers ( I?, 20,2 1).
METHODS This case-referent study includes salivary gland cancer cases and a population comparison group from the Occupational Cancer Incidence Surveillance Study (CCISS) (22), a population-based investigation of occupational risk factors for cancers diagnosed among residents of the tri-county Detroit area. Cancer cases were identified through the Metropolitan Detroit Cancer Surveillance System, a participant in the SEER program. A rapid reporting system was utilized to enroll cancer case subjects within 2-6 weeks after diagnosis. Incident salivary gland cancer cases in this study were diagnosed between November 1984 and Match 1991. Subjects
370
AEP Vol. 7, No. 6 AugUst 1997: 369-374
Swanson and Burns SALIVARY GLAND CANCER IN THE WORKPLACE
Selected
Abbreviationsand Acronyms
SEER = Surveillance, Epidemiology, and End Results Program OCISS = Occupational Cancer Incidence Surveillance Study OR = odds ratio CI = confidence interval
in the population comparison group were selected by random-digit dialing (23). Occupations categorized as unexposed for this study included such groups as housewives, administrators, teachers, and clerical workers. Examples of industries categorized as unexposed are real estate, schools, banks, and department stores. A more detailed description of the OCISS is found in an earlier report (22). This study includes black and white men and women in the group aged 40-84 years: 163 persons with salivary gland cancers and 375 1 population referents. Subjects or their surrogates (spouse or other first+degree relative of the subject) were interviewed by telephone. The interview obtained info~ation on lifetime occupational history, lifetime smoking history, adult medical history, residential history, education, birthplace, and other demographic variables. The response rates for casesand the comparison group were 94% and 97%, respectively. Occupation and industry data obtained by the telephone interview were coded according to the 1980 U.S. Census Bureau classification codes (24). Grouped codes were created by combining codes for specific occupations or induse tries characterized by similarities in work exposures. Before analysis, an unexposed group was defined by selection of occupations and industries with little or no exposure to carcinogens (22). All other occupations and industries were considered exposed to some form of potentially carcinogenic substance for the analysis, Work histories were evaluated on the basis of a subject reporting ever having been employed in a particular occupation or industry. Maximum likelihood estimates of the odds ratio (ORs) for ever smoking and for occupations and industries were obtained from multiple logistic regression analyses (25). The risk of occurrence of salivary gland cancers by smoking status was estimated by comparison of smokers with nonsmokers. The potential confounding effects of age at diagnosis, gender, and race were controlled for in the analysis. The risk of occurrence of salivary gland cancers among exposed occupations and industries was estimated in comparison to this risk among subjects who were employed solely in unexposed occupations and industries during their lifetime. Analyses were performed separately for men and women. The potential confounding effects of age, cigarette smoking, and race were controlled for in the model. The ORs and their respective confidence intervals were calculated for each occupa+ tion and industry category that included at least five cases.
RESULTS Table 1 includes the distribution of Occupational Cancer Incidence Surveillance System salivary gland cancers by anatomic site and histologic type. The predominant anatomic site for salivary gland cancers was the parotid gland, while the most common cell type was mucoepidermoid carcinoma. There is little difference between men and women in the specific anatomic site; however, there are differences in the histologic type, with women having a greater proportion characterized as acinar cell adenomas, whiie men have a greater proportion identified as squamous cell carcinoma or adenocarcinoma. Table 2 presents the distribution of salivary gland cancers and population referents by demographic and smoking characteristics. Women and men diagnosed with cancers of the salivary gland were younger than the population comparison group and included a higher proportion of whites. Most interviews were conducted with subjects directly for both cases (77.3%) and contrdls (92.0%). Among cases, interviews were conducted with next-of-kin proxies for 14.1% of participants who were alive but too ill to respond by interview and for 8.6% who were deceased at time of interview. Among controls, 7.9% of interviews were conducted with proxies when controls were alive but too ill for interview, and less than 1% were conducted among proxies for deceased controls. Comparison of cigarette smoking status between persons diagnosed with salivary gland cancers and the population referents revealed a significant elevated OR among persons with 80 pack-years or more of cigarette smoking (Table 3). Table 4 presents the risk of occurrence of salivary gland cancers by occupation. A statistically significant elevated odds ratio is observed among women ever employed as hairdressers (OR, 2.7; 95% confidence interval (CI), 1.1-6.5). The mean number of months of employment as a hairdresser was 97.7. Two women were employed for > 15 years as hairdressers, one for 6 years, and four for 6 2 years. Only two of these women had ever smoked cigarettes. Other occupations with ORs of > 2.0 include women ever employed as stock clerks (OR, 2.8; 95% CI = 1.0-8.0) and men ever employed as machine repairers (OR, 3.6; 95% CI = 0.7, 18.9). Table 5 describes the risk of salivary gland cancer by industry. The OR is statistically significantly elevated among women ever employed in beauty shops (OR, 3.4; 95% CI = 1.4-7.9). Other industries for which the OR is > 2.0 include men ever employed in the railroad industry (OR, 5.3; 95% CI, 0.5-55.6), oil and gassales (OR, 3.8; 95% CI, 0+4-32.8), and the post office (OR, 3,l; 95% CI, 0.3-30.0).
DISCUSSION A clear observation in this study is the association between employment in hairdressing and the occurrence of cancers
TABLE 1. Distribution of cancersof the salivary gland included in OCISS by gender, anatomic site, and histologic type --.__ Male Cancer
Female
NO.
%
No.
Site Parotid S&man&h&x Suhhngual Major salivary glands, NOS Tt ml
64 15 3 2
76.2 17.9 3.6 2.4
hi 13 4
Histc&>gtc Type Mucoe~~dermoid carcinoma Squamous cell carcinoma Ailmwxcmoma Acinar cell adenuma Adenoid cystic carcinoma Orhcr Tml
16 18 18 7 6 19
19.0 21.4 21.4 8.3 21.7 22.6
TABLE 2. Distribution of salivary gland cancer casesand population referents by race, age,gender, smoking status, and pack-yearsof smoking Population referents
Salivary gland cancer cases Group
NO.
5%
NO.
%
Race White Black U&et
141 19 3
86.5 11.7 1.8
2955 795 1
78.8 21.2 0.0
-I-mr i
163
100.0
3751
100.0
Age 40-49 50-59 6049 m-79 PO-84 Unknown
16 32 56 47 8 4
9.8 19.6 34.4 28.8 4.9 2.5
275 697 1336 1108 332 3
7.3 18.6 35.6 29.5 8.9 0.1
TCK:Il
163
100.0
3751
100.0
Getlifer Male Fetnale
84 79
il.5 48.5
1807 1944
48.2 51.8
Torai
163
100.0
3751
100.0
96 67
58.9 41.1
2131 1620
56.8 43.2
Total
163
--.-. NC’ --’
77.2 lb.5 5.1 I.3
76.7 17.2
4.3 I.8 I:@.0
]I’,’
of the salivary gland. This finding was apparent whether the analysis was performed for the occupational category of hairdressing or the industry category of beauty shop. This association represents a new observation, since previous studies concerned with cancer risks among hairdressers have not included any cases of salivary gland cancers (26, 27). A related study, not focused upon occupational exposure,
Smoking status Ever smoked Never smoked
P’(Tdl 041
100.0
3751
100.0
19 8 8 15 1C t9
1’4.0 10.1 10.1 19.1 12.7 24.0
did observe an association between the ~.tseof hair dyes and cancers of the saGvary gland (16). Beauticians are exposed to various chemicals, including hair sprztvs and permanent and wave solutions. Women employed as stock clerks alst: had an elevated odds ratio. Exposures in this occupatior? are likely to be diverse and require more thorough assessment. Potential leads concerning the occu~~~ri~~naletiology of salivary gland cancers among men include the occupation of machine repairer as well as jobs in the railroad, gas and oil sales,and post office industries. Each of these work situations involve potential exposure to motor exhaust. With the exception of post of&e workers, people in these occupations aiso are likely to have some exposure to qc?lvents and cutting oils. A common thread in all of the occuparlrms and industries among which this study observed elevated risk of cancers of the salivary gland is exposure to inhale’3 chemicals, fumes, and sprays. This route of exposure is the: most plausible for the anatomic sites encompassed in rhe catt:g
TABLE 3. Risk of salivary gland czmcerby Ix+&-yearsof cigarette smoking --..No.
of
Smokmg status1
CZWS
Referents
Non-smoker < 20 pack years Z&39 pack years 40-59 pack years 60-79 pack years
67 23 21 22 6
IhZC 656 5% 436 188
3 80 pack years
18
225
95% i ‘U,.iz Confidence f!~lrM, Interval .~ 6 eferent Cin~p 5’3 O-i-1.4 .,’ t ’ 0.6-1.5 !.I O.?-?.<) \“iI. O.2- I.6 i.h
1.0-1.3
*There were four cases and 39 referentc frlr whanl numhcr ,\1’pack-year* was unknown.
372
AEP Vol. 7, No. 6 August 1997: 369-374
Swanson and Bums SALIVARY GLAND CANCER IN THE WORKPLACE
TABLE 4.
Risk of salivary
gland cancer by occupation No. of
Occupation, exposure
Cases
Referents
Men” Agricultural worker Laborer Assembler Janitor Mechanic Machine repair Tool and die worker Metal finisher Machine operator Driver Military Unexposed
10 10 18 6 13 7 7 7 8 9 52 3
186 312 404 146 147 83 193 260 153 209 1054 58
Women” Stock clerk Assembler Quality control checkers Private household service Hairdressers Health technicians Foodworkers Unexposed
5 10 5 9 7 7 5 34
35 154 90 210 56 138 181 809
Odds ratio
95% Confidence interval
1.1 0.8 0.9
0.2-4.2 0.2 3.2 0.2-3.2 0.3-7.9 0.5-7.7 0.7-18.9 0.2-3.4 0.2-2.4 0.3-4.8 0.2-3.3 0.3-2.9
2.8 1.6 1.4 0.7 2.7 1.0 0.5
1.0-8.0 0.8-3.4 0.5-3.9 0.3-1.7 1.1-6.5 0.4-2.4 0.2-1.3
1.0 0.8 0.9 1.6 1.9 3.6 0.8
0.5
a Blacks and whites combined.
glands because they are all located in the area of the head and neck. Previous studies have suggestedthat workplace exposures may increase the risk of salivary gland cancers. Some of
salivary
TABLE 5.
Risk of salivary
these studies have focused upon occupational exposure to radiation, including exposure of fluorospar miners to radon progeny and employment at the Lawrence Livermore National Laboratory (28, 29). There is also a suggestion of a
gland cancer by industry No. of
Industry exposure
Odds ratio
95% Confidence interval
Cases
Referents
Men” Farming Construction Automobile manufacturing Railroad Post office Food store Oil and gas sales Military Unexposed
10 9 40 5 5 5 8 52 2
184 293 971 33 78 114 73 1063 36
1.6 1.9 1.7 5.3 3.1 1.4 3.8 1.8
0.2-13.8 0.2-16.6 0.2-12.7 0.5-55.6 0.3-30.0 0.2 14.0 0.4-32.8 0.2-13.5
Women” Automobile manufacturing Private household Laundry/dry cleaning Beauty shop Medical office Hospital Unexposed
19 9 5 8 5 7 24
341 226 85 61 76 231 605
1.6 0.8 1.4 3.4 1.7 0.8
0.3-3.0 0.3-1.9 0.5-3.8 1.4-7.9 0.6-4.7 0.3-1.9
a Blacks and whites combined
AEP b’& 7, NIX 6 Auffltsr 1997: 369-374
relationship between salivary gland cancers and asbestos mining (30) and employment in rubber products manufacturing plants (2 1f . High rates of salivary gland cancers have been found among workers in livestock-feed processing companies in Denmark (3f), among workers employed in a mustard-gas manufacturing plant in England during Worfd War II (32) , and among underground colliery workers in Australia (33). A study in several automobile plants in the Detroit metropolitan area found an increase in salivary gland cancer among woadworkers (20). Two salivary gland cancers were observed among automotive woodworkers when fewer than one case was expected. An increase in salivary gland cancers among woodworkers was not observed in our study. In an analysis not shown, cancer risks in occupations within the auromobile industry were assessed,and no increase in risk was observed among woodworkers in the automobile industry. In contrast to previous observations, this study found an association between cigarette smoking and the occurrence of cancers of the safivary gland. This association was observed only among those with the highest level of exposure to cigarette smoking: 3 80 pack-years. Therefore, it will be important for future studies of the etiology of salivary gland cancers to evaluate this relationship further. The resuks of the study are limited by the lack of information on specific exposures in the workpiace and outside of work. OCISS was designed to evaluate occupationa risks for eleven cancer sites, encompassing => 20,000 subjects. Therefore, obtaining information about specific exposures for an individual cancer sire was not practical. Although a larger proportion of case than control interviews were conducted among proxies, the information provided regarding occupational history and cigarette smoking is simifar in completeness and detail to that provided by subjects themselves. This would suggest that the next-of-kin respondents can provide such information. Although we assume that such ~~~f~~rrnat~on is accurate, we have no secondary source of data against which to validate these responses. The limitations of the data are offset by the many strengths of the study. These include the detailed occupation and smoking hisrories ubtained, the use of population-based cases and controls, and the high response rate. Much of the research regarding salivary gtand cancers has focused on radiation exposure (7-17). Atomic bomb survivors (9, 10) and patients exposed to radiation for medical conditions or diagnosric purposes (7, 8, 1l-13, 15-17) have consistently shown an increased risk of salivary gland cancers and other head and neck cancers. Radiation therapy for chitdhood diseases,such as ringworm, which were treated by irradiation of the head and neck area, is implicated in the etiology of salivary gland cancers (8,11,34). In addition, adults who underwent radiation therapy to the head and neck, face, or upper torso, often for conditions such as acne,
eczema, and hair removal, have been observed to experience excess rates of salivary gland cancers (3, 7, /3, 16, 17). Exposure to diagnostic radiation for medical and dental assessments has been implicated in the etiology of these cancers as welt (15 1.The present study could not addressthis issue because such exposure information was not collected during the interviews. Several studies have found that patients previously diagnosed with skin cancers have high rates s>fsubsequent cancers of the salivary gland (35,361. It is hy~thes~~ed that this association may result from exposure to ultraviolet radiation (14, 36). In the present study, no association was observed between employment in which radiation exposure was likely to have occurred and the occurrence of salivary gland cancers. The increased risk of salivary gland cancer among women employed in beauty shops is intriguing. Further investigation should identify the specific exposures involved, which may include permanent and wave-setting solutions, hair dyes, or hair sprays. The results of this study &o strorrgiy suggest that the understanding of the etiology of cancers of the salivary gland may be enhanced by focusing upon inhaled exposures (e.g.* motor exhaust, fumes, and sprays). Our observations suggesttwo directions for future research: (i) analysis of specific exposures experienced Fy hairdressers while they are engaged in this work activity, pe&aps in a ‘largercase referent study; and (ii) assessmenri:i rhe role c,Etobacco use by gender, age, histologic type, ant1 ~~ccl~pation in a larger case-referent study. -----REFERENCES 1.
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314
Swanson and Bums SALIVARY GLAND CANCER IN THE WORKPLACE
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epidemiologicat