#63 Cancer incidence in the u. s. radiologic technologists health study, 1983–1998

PURPOSE: Few studies have evaluated cancer risk associated with low-dose occupational ionizing radiation exposure to women. We present data on incident cancer risks among a predominantly (77%) female cohort of 73,963 U. S. radiologic technologists followed up from 1983 through 1998.METHODS: Cancer incidence information and data on work history, selected cancer risk factors, personal radiation exposure and other health outcomes were obtained from two mailed questionnaires (administered ~1984 and ~1995). Incident cancers were ascertained from the second survey and supplemented by mortality records. Medical records, obtained for 74% of all self-reported cancers, confirmed the cancer in 85%. We computed standardized incidence ratios (SIR) using cancer incidence rates from the National Cancer Institute's Surveillance Epidemiology and End Results Program.RESULTS: The SIR for all cancers combined in both sexes was 1.04 (95% confidence interval (CI): 1.00, 1.07; n = 3292). The incidence of solid cancers was elevated in women (SIR = 1.06, 95% CI: 1.02, 1.10), but lower than expected among men (SIR = 0.92 , 95% CI 0.85, 0.98). Female technologists had an elevated incidence of breast cancer (SIR = 1.16, 95% CI: 1.09, 1.23). Among both sexes combined, elevated risks were seen for melanoma (SIR = 1.59, 95% CI: 1.38, 1.80) and thyroid cancers (SIR = 1.61, 95% CI: 1.34, 1.88), and decreased risks were observed for buccal cavity/pharynx (SIR = 0.73, 95% CI: 0.55, 0.90), rectum (SIR = 0.62, 95% CI: 0.48, 0.76), and lung (SIR = 0.77, 95% CI: 0.70, 0.85) cancers.CONCLUSION: The elevated risk for breast cancer may be related to occupational radiation exposure. The observed melanoma and thryoid cancer excesses may reflect, at least in part, increased screening among medical workers with easy access to health care.     

Are patients with skin cancer at lower risk of developing colorectal or breast cancer?

Ultraviolet exposure may reduce the risk of colorectal and breast cancer as the result of rising vitamin D levels. Because skin cancer is positively related to sun exposure, the authors hypothesized a lower incidence of breast and colorectal cancer after skin cancer diagnosis. They analyzed the incidence of colorectal and breast cancer diagnosed from 1972 to 2002 among 26,916 Netherlands skin cancer patients (4,089 squamous cell carcinoma (SCC), 19,319 basal cell carcinoma (BCC), and 3,508 cutaneous malignant melanoma (CMM)). Standardized incidence ratios were calculated. A markedly decreased risk of colorectal cancer was found for subgroups supposedly associated with the highest accumulated sun exposure: men (standardized incidence ratio (SIR) = 0.83, 95% confidence interval (CI): 0.71, 0.97); patients with SCC (SIR = 0.64, 95% CI: 0.43, 0.93); older patients at SCC diagnosis (SIR = 0.59, 95% CI: 0.37, 0.88); and patients with a SCC or BCC lesion on the head and neck area (SIR = 0.59, 95% CI: 0.36, 0.92 for SCC and SIR = 0.78, 95% CI: 0.63, 0.97 for BCC). Patients with CMM exhibited an increased risk of breast cancer, especially advanced breast cancer (SIR = 2.20, 95% CI: 1.10, 3.94) and older patients at CMM diagnosis (SIR = 1.87, 95% CI: 1.14, 2.89). Study results suggest a beneficial effect of continuous sun exposure against colorectal cancer. The higher risk of breast cancer among CMM patients may be related to socioeconomic class, both being more common in the affluent group.     

Hip fractures in women with breast cancer

The authors investigated whether the incidence of first hip fracture, an indicator of osteoporosis, is lower in breast cancer patients, who are assumed to have higher levels of endogenous estrogens, than in other women. A population-based Swedish cohort comprising 9,673 women with invasive breast cancer diagnosed from 1958 through 1983 was followed up with respect to the occurrence of a first hip fracture during the period 1965-1983. Overall, the number of observed acute fractures (n = 387) was slightly higher than expected (n = 348.6) (standardized incidence ratio (SIR) = 1.1, 95% confidence interval (CI) 1.0-1.2). Risk for trochanteric fractures was slightly higher than expected (SIR = 1.2, 95% CI 1.0-1.4), but risk for cervical fractures was not (SIR = 1.0, 95% CI 0.9-1.1). Risk for trochanteric fracture decreased with increasing age at breast cancer diagnosis, reaching standardized incidence ratios close to unity after the age of 70 years. Duration of follow-up appeared to be unrelated to the risk of either type of fracture. The authors conclude that the incidence of first hip fracture is not lower in breast cancer patients than in other women.     

Cancer incidence rates among Lawrence Livermore National Laboratory (LLNL) employees: 1974-1997

BACKGROUND: In the mid-1970's an excess of malignant melanoma of the skin was noted among employees at the Lawrence Livermore National Laboratory (LLNL). A 1984 cancer incidence study showed a non-significant excess of total cancers among female employees with significant excesses for melanoma, rectum and anus, and salivary gland cancers. For male employees, there was a non-significant deficit of total cancer with significant excesses in melanoma and non-brain nervous system cancers. This paper reports the results of a surveillance effort to update our understanding of the patterns of cancer incidence in this population. METHODS: We used California Cancer Registry (CCR) data to ascertain employees who had worked for six or more consecutive months at LLNL during the 24-year period of 1974 through 1997 who were diagnosed weith cancer during that time frame. We used the Standardized Incidence Ratio (SIR) in our analyses. RESULTS: There were 17,785 employees who provided 186,558 person-years of observation: 145,203 were from males and 41,355 were from females. The CCR, through its linkage techniques, identified 541 individuals with invasive cancer and 96 with in situ cancer. A total of 404 males had invasive cancer and 33 had in situ cancer whereas there were 137 females with invasive cancer and 63 with in situ cancer. The SIR for invasive cancer in males was 69 (95% CI 62-76). The overall cancer SIR for males was unaffected by calendar time. There were only two invasive cancer sites with significant excess: melanoma and cancer of the testes. For eight categories or cancer sites, we found a statistical deficit in cancer incidence. The most striking deficit occurred in cancer of the lungs and bronchus with a SIR of 36 (95% CI 26-50). The SIR for invasive cancer in females was 80 (95% CI 67-94). The overall cancer SIR for females decreased over calendar time. There was a statistically significant deficit for cancers of the female genital organs. There were 84 cases of invasive and in situ melanoma in both genders. Time-trend analyses for melanoma showed a significant excess during the years 1974-1985 but a reduction to community rates from 1986 through 1997. There were 21 individuals with testicular cancer with a SIR of 207 (95% CI 129-317). There were no differences in age at diagnosis or cell type with the comparison population. We analyzed the data using the same radiosensitive cancer categories used in the 1984 study. There were no increases in SIRs in any of these categories. CONCLUSIONS: We found that the LLNL employees had less cancer than expected with males having relatively fewer cancers than females. The lung cancer rate for males was remarkably low. Since 1986 the melanoma rates resemble the community rates. Testicular cancer rates are modestly elevated and appear to have been so for the past 20 years. Lifestyle patterns, including smoking, and cancer screening activities are probably important contributors to the observed low cancer rates.     

Second primary ovarian cancer among women with cancer

PURPOSE: Some studies suggest women with certain types of cancers are at increased risk for ovarian cancer. This study assessed the risk of second primary ovarian cancer among U.S. women who have cancer by anatomic site, age, race, and time since diagnosis of the first primary cancer.METHODS: We analyzed data from SEER cancer registries for women diagnosed with invasive cancer between 1973 and 1996. Person-years were accumulated from 2 months after initial cancer diagnosis to date of ovarian cancer diagnosis, death, loss to follow-up, or end of follow-up, December 31, 1996. The expected number of cases was obtained by multiplying 5-year age and calendar year interval specific ovarian cancer rates by the accumulated person-years at risk. We calculated the risk (observed [O]/expected numbers [E]) of second primary ovarian cancer by cancer site and age (<50 years, >/=50 years), race (all, white, black), and time since first cancer (0-4, 5-9, 10-14, 15-24 years). Statistical tests and 95% confidence intervals (CI) were based on the assumption of a Poisson distribution.RESULTS: A significant increased risk of ovarian cancer was found for women aged <50 years at time of diagnosis with melanoma (O/E = 3.5, 95% CI = 2.1-5.5) and cancer of the breast (O/E = 6.0, 95% CI = 4.9-7.2), cervix (O/E = 4.2, 95% CI = 2.6-6.3), corpus uteri (O/E = 11.91, 95% CI = 7.3-18.4), colon (O/E = 17.9, 95% CI = 11.1-27.3), and ovary (O/E = 4.9, 95% CI = 2.7-8.2); no increased risk was found for women aged >/=50 years. Ovarian cancer risk remained elevated following all of these first primary cancers 5-9 years after diagnosis; for women with breast and colon cancer, risk remained elevated 15-24 years after diagnosis. A significant increased risk was found for all of these cancers among white women <50 years at diagnosis; risk was increased among black women <50 years with cancer of the breast, cervix, and colon.CONCLUSIONS: We found an ovarian cancer risk higher than expected for women with certain types of cancer; however, the risk was limited to women <50 years of age.     

Cancer incidence among Norwegian airline cabin attendants

BACKGROUND: Cabin crews are exposed to cosmic radiation at work and this may increase their incidence of radiation-induced cancers. Former studies indicate an increased risk of breast cancer. METHODS: A retrospective cohort study was performed. The cohort was established from the files of the Civil Aviation Administration and included people with a valid licence as a cabin attendant between 1950 and 1994. The cohort was linked to the Cancer Registry of Norway. Observed number of cases was compared with expected, based on national rates. Breast cancer incidence was analysed, adjusting for individual fertility variables. RESULTS: A group of 3693 cabin attendants were followed over 72 804 person-years. Among the women, 38 cases of breast cancer were observed (standardized incidence ratio (SIR) = 1.1, 95% CI : 0.8-1.5). Among men excess risks were found for cancers in the upper respiratory and gastric tract (SIR = 6.0, 95% CI : 2.7-11.4) and cancer of the liver (two cases, SIR = 10.8, 95% CI : 1.3-39.2). For both sexes elevated risks were found for malignant melanoma and non-melanoma skin cancer; for men these were SIR = 2.9 (95% CI : 1.1-6.4) and SIR = 9.9 (95% CI : 4.5-18.8) respectively, while for women these were SIR = 1.7 (95% CI : 1.0-2.7) and SIR = 2.9 (95% CI : 1.0-6.9) respectively. For no cancer site was a significant decreased risk found. CONCLUSIONS: An increased risk of radiation-induced cancers was not observed. The excess risks of some other cancers are more probably explained by factors related to lifestyle.     

Radioactive iodine therapy and breast cancer. A follow-up study of hyperthyroid women

A follow-up study of 1,762 hyperthyroid women who were treated at the Massachusetts General Hospital Thyroid Unit between 1946 and 1964 was conducted. The average length of follow-up was 17.2 years. A 1978 mailing address or a death certificate was located for 92% of the women, and 88% of 1,058 living patients responded to a mail questionnaire. The standardized mortality ratio (SMR) for all causes of death was 1.3 (95% confidence interval (CI) 1.2-1.4). The standardized mortality ratios for all malignant neoplasms and for breast cancer were 0.9 (95% CI 0.7-1.1) and 1.3 (95% CI 0.8-1.9), respectively. More deaths than expected were observed from endocrine and metabolic diseases (SMR = 1.8, 95% CI 1.2-2.7), circulatory system diseases (SMR = 1.4, 95% CI 1.3-1.6), and respiratory system diseases (SMR = 1.9, 95% CI 1.3-2.6). The standardized incidence ratios (SIR) for all malignant neoplasms and for breast cancer were 0.9 (95% CI 0.8-1.1) and 1.2 (95% CI 0.9-1.5), respectively. A nonsignificant excess breast cancer risk was observed 10 years after the onset of thyroid symptoms and was present at the end of 30 years of observation. A statistically significant excess number of pancreatic cancer cases (SIR = 2.0, 95% CI 1.0-3.7) and a nonsignificant excess of brain cancer cases (SIR = 2.3, 95% CI 0.7-5.3) were observed. Eighty per cent of the women were treated with radioactive iodine. When age at treatment and year of treatment were controlled, women who were ever treated with radioactive iodine had a standardized rate ratio for breast cancer of 1.9 (95% CI 0.9-4.1), compared with those who were never treated with radioactive iodine. Women who developed hypothyroidism as a result of their treatment for hyperthyroidism did not have an increased risk of developing breast cancer (SIR = 1.1, 95% CI 0.8-1.6).     

Cancer risk among 43000 Norwegian nurses

OBJECTIVES: This study evaluated the influence of occupational exposure on cancer risk among female Norwegian nurses. METHODS: A historical prospective cohort study was performed. The cohort was established from the Norwegian Board of Health's registry of nurses and included women who graduated from a nursing school before 1985. The cohort (N=43 316) was linked to the Cancer Registry of Norway. The observed number of cases was compared with the expected number on the basis of national rates. Time since first employment, period of first employment, and duration of employment were used as indicators of exposure. Poisson regression analyses were used for internal comparisons, adjusting for age, period, and fertility. RESULTS: The nurses were followed over 1473931 person-years. During the follow-up (1953-2002), 6193 cancer cases were observed. The standardized incidence ratio (SIR) for all cancers combined was close to unity. Significantly lower risks were found for cancers with a known association with alcohol and tobacco consumption and sexual activity. A significantly increased risk was found for breast cancer (SIR 1.14, 95% confidence interval (95% CI) 1.09-1.19), ovarian cancer (SIR 1.14, 95% CI 1.04-1.25), malignant melanoma (SIR 1.15, 95% CI 1.04-1.28), and borderline significant risk appeared for other skin cancer (SIR 1.12, 95% CI 0.98-1.29). A positive trend for increasing time since first exposure was found for breast cancer and malignant melanoma. CONCLUSIONS: The results indicate an association between working as a nurse and an increased risk of breast cancer and malignant melanoma. Decreased risks, found for several cancers, indicate favorable lifestyle habits among nurses.     

Second primary cancers following anal and cervical carcinoma: evidence of shared etiologic factors.

The authors examined the incidence of second primary cancers occurring after cervical and anal cancer. Data from the Connecticut Tumor Registry for 1935-1988 and eight other US tumor registries for 1973-1988 were used. Women with primary invasive cervical cancer had a relative risk of 4.6 (95% confidence interval (CI) 2.4-8.1) for subsequent invasive anal cancer. Increased relative risks after cervical cancer were also found for cancers of the oral cavity (relative risk (RR) = 2.2), stomach (RR = 1.5), rectum (RR = 1.4), larynx (RR = 3.4), lung (RR = 3.0), vagina (RR = 5.6), bladder (RR = 2.7), for kidney (RR = 1.9); decreased relative risks were noted for melanoma (RR = 0.5) and breast cancer (RR = 0.8). Patients with a primary diagnosis of anal cancer had relative risks for subsequent invasive and in situ cervical cancer of 1.3 (95% CI 0.2-4.5) and 3.4 (95% CI 0.9-8.8), respectively. Anal cancer was also associated with increased relative risks of subsequent lung (RR = 2.5) and prostate (RR = 1.8) cancers, whereas the relative risk of uterine cancer was 0.2 (95% CI 0.0-0.9). These findings support other evidence for common factors, such as human papillomavirus infection and cigarette smoking, in the etiology of cervical and anal cancer.     

The contribution of risk factors to the higher incidence of invasive and in situ breast cancers in women with higher levels of education in the European prospective investigation into cancer and nutrition

The authors investigated the role of known risk factors in educational differences in breast cancer incidence. Analyses were based on the European Prospective Investigation Into Cancer and Nutrition and included 242,095 women, 433 cases of in situ breast cancer, and 4,469 cases of invasive breast cancer. Reproductive history (age at first full-term pregnancy and parity), exposure to endogenous and exogenous hormones, height, and health behaviors were accounted for in the analyses. Relative indices of inequality (RII) for education were estimated using Cox regression models. A higher risk of invasive breast cancer was found among women with higher levels of education (RII = 1.22, 95% confidence interval (CI): 1.09, 1.37). This association was not observed among nulliparous women (RII = 1.13, 95% CI: 0.84, 1.52). Inequalities in breast cancer incidence decreased substantially after adjusting for reproductive history (RII = 1.11, 95% CI: 0.98, 1.25), with most of the association being explained by age at first full-term pregnancy. Each other risk factor explained a small additional part of the inequalities in breast cancer incidence. Height accounted for most of the remaining differences in incidence. After adjusting for all known risk factors, the authors found no association between education level and risk of invasive breast cancer. Inequalities in incidence were more pronounced for in situ breast cancer, and those inequalities remained after adjustment for all known risk factors (RII = 1.61, 95% CI: 1.07, 2.41), especially among nulliparous women.     

Cancer incidence after nasopharyngeal radium irradiation

BACKGROUND: From 1940 until 1970, nasopharyngeal radium irradiation was used to treat children and military personnel suffering from Eustachian tube failure attributable to local lymphoid hyperplasia. METHODS: We studied cancer incidence in a cohort of 4339 Dutch patients treated with nasopharyngeal radium irradiation, mostly in childhood, and 4104 frequency-matched nonexposed subjects. Average doses to the nasopharynx, pituitary gland, brain, and thyroid gland were 275, 10.9, 1.8, and 1.5 cGy, respectively. We assessed cancer incidence from cancer registry linkage (1989-1996), self-report including medical verification (1945-1988), and death certificates (1945-1996). RESULTS: During 18-50 years of follow-up, four thyroid malignancies (standardized incidence ratio [SIR] = 2.8; 95% confidence interval [CI] = 0.8-7.2) and five malignant brain tumors (SIR = 1.3; CI = 0.4-3.1) were observed. Increased risks were observed for malignancies of lymphoproliferative and hematopoietic origin (SIR = 1.9; CI = 1.2-2.8) and breast cancer (SIR = 1.5; CI = 1.1-2.1). Strong dose-response trends could not be demonstrated for any cancer outcome, although relative risk estimates were elevated in the highest-dose category for head and neck cancer and breast cancer. CONCLUSIONS: These data provide little evidence for a high excess risk of cancer associated with nasopharyngeal radium irradiation treatment as applied in the Netherlands. Inconsistent findings across studies and public concern warrant the continuing follow-up of available cohorts.     

Thyroid cancer incidence in Chornobyl liquidators in Ukraine: SIR analysis, 1986–2010

We studied thyroid cancer incidence in a cohort of 150,813 male Chornobyl clean-up workers (“liquidators”) from Ukraine by calculating standardized incidence ratio (SIR) using national cancer statistics. Follow-up began on the liquidator’s registration date with the Chornobyl State Registry of Ukraine (the earliest date was 05. 05. 1986) and continued through December 31, 2010, date of thyroid cancer diagnosis, date of death, or date of last known vital status, whichever came first. There were 196 incident thyroid cancers in the study cohort with an overall SIR of 3.50 [95 % confidence interval (CI) 3.04–4.03]. A significantly elevated SIR estimate of 3.86 (95 % CI 3.26–4.57) was observed for liquidators who had their first clean-up mission in the Chornobyl zone in 1986, when levels of external and internal exposure to radiation were highest; the SIR estimates for later calendar years of first clean-up mission, while significantly elevated, were lower. The SIR estimates were elevated throughout the entire follow-up period but were especially high 10–18 years after the accident: 4.62 (95 % CI 3.47–6.15) and 4.80 (95 % CI 3.78–6.10) for the period 1995–1999 and 2000–2004, respectively. Our findings support the growing evidence of increased thyroid cancer rates among Chornobyl liquidators. Although this could be partially attributed to increased medical surveillance, the observed pattern of SIR increase warrants further investigation of a potential contribution of radiation exposure to the elevated thyroid cancer rates in this large population.     

Cancer incidence in airline cabin crew: experience from Sweden

Aims: To determine the cancer incidence in Swedish cabin crew.

Methods: Cancer incidence of cabin crew at the Swedish Scandinavian Airline System (SAS) (2324 women and 632 men) employed from 1957 to 1994 was determined during 1961–96 from the Swedish National Cancer Register. The cancer incidence in cabin crew was compared with that of the general Swedish population by comparing observed and expected number of cases through standardised incidence ratios (SIR). A nested case-control study was performed, including cancer cases diagnosed after 1979 and four controls per case matched by gender, age, and calendar year.

Results: The SIR for cancer overall was 1.01 (95% CI 0.78 to 1.24) for women and 1.16 (95% CI 0.76 to 1.55) for men. Both men and women had an increased incidence of malignant melanoma of the skin (SIR 2.18 and 3.66 respectively) and men of non-melanoma skin cancer (SIR 4.42). Female cabin attendants had a non-significant increase of breast cancer (SIR 1.30; 95% CI 0.85 to 1.74). No clear associations were found between length of employment or cumulative block hours and cancer incidence.

Conclusions: Swedish cabin crew had an overall cancer incidence similar to that of the general population. An increased incidence of malignant melanoma and non-melanoma skin cancer may be associated with exposure to UV radiation, either at work or outside work. An increased risk of breast cancer in female cabin crew is consistent with our results and may in part be due to differences in reproductive history.

     

Active and passive smoking in breast cancer: prospective results from the Nurses' Health Study

BACKGROUND: The role of active and passive smoking in breast cancer remains controversial. METHODS: Using data collected in the prospective Nurses' Health Study, we examined the influence of active and passive smoking on the incidence of invasive breast cancer. The analysis was based on women responding to the 1982 questionnaire, which included questions on passive smoking exposure. Information on active smoking was collected in biennial questionnaires. A total of 78,206 women were followed prospectively from 1982 until June 1996. RESULTS: Of these women, 3,140 reported a diagnosis of invasive breast cancer during follow-up. Compared with never active smoking, relative risks (RR) of breast cancer were 1.04 (95% CI = 0.94-1.15) for current active smoking and 1.09 (95% CI = 1.00-1.18) for past active smoking. The RR for regular passive exposure at work and at home was 0.90 (95% CI = 0.67-1.22). For active smoking, a modest increase in risk was confined to women who began smoking before the age of 17 (RR = 1.19; 95% CI = 1.03-1.37). CONCLUSION: Results suggest that passive smoking is unrelated to breast cancer. However, results for active smoking are compatible with a small increase in risk when smoking is initiated at young ages.     

Cancer in husbands of cervical cancer patients

We used the Swedish Family-Cancer Database to analyze the spectrum of cancers diagnosed in husbands of women with in situ or invasive cervical cancer, and we compared these to second carcinogenic events in women presenting with these cancers. Our hypothesis was increased cancer susceptibility from human papilloma virus (HPV). When the wives had in situ or invasive cervical cancer, the standard incidence ratios (SIRs) for anal cancer in husbands were 1.75 (95% CI = 1.05-2.62) and 1.92 (95% CI = 0.69-3.76). Anal cancer was also increased as a second primary cancer in women. Other common cancers were related to tobacco smoking. The results indicate that HPV infection is associated with anal cancer in both men and women.     

Cancer among women textile workers in Shanghai, China: overall incidence patterns, 1989-1998

BACKGROUND: Cancer incidence in women textile workers has not been adequately studied. The aim of this study was to examine site-specific cancer incidence patterns in a cohort of 267,400 women textile workers in Shanghai, China. METHODS: Women employed by the Shanghai Textile Industry Bureau (STIB) were followed for cancer incidence from 1989 to 1998. Age-adjusted standardized incidence ratios (SIRs) and 95% confidence intervals (CI) were computed based on Shanghai Cancer Registry (SCR) rates. RESULTS: There was a decrease in cancer incidence for the cohort compared with urban Shanghai women (SIR = 0.91, 95% CI = 0.89-0.93). There were small increased risks of other endocrine tumors (SIR = 1.31, 95% CI = 1.02-1.65). There were decreased risks for esophageal (SIR = 0.54, 95% CI = 0.44-0.66), stomach (SIR = 0.79, 95% CI = 0.73-0.85), rectal (SIR = 0.88, 95% CI = 0.78-0.98), lung (SIR = 0.80, 95% CI = 0.74-0.86), cervical (SIR = 0.37, 95% CI = 0.28-0.50), ovarian (SIR = 0.85, 95% CI = 0.75-0.96), and bladder cancers (SIR = 0.63, 95% CI = 0.46-0.85). CONCLUSIONS: Women employed in the textile industry had a lower than expected cancer experience compared with urban Shanghai women. Further research on this cohort will examine associations between site-specific cancers and occupational exposures to dusts and chemicals.     

Cancer incidence in a cohort of infertile women

To explore further the relation between infertility and breast and female reproductive cancers, cancer incidence among 2,632 Israeli women treated for infertility between 1964 and 1974 was evaluated. Cancer incidence through December 1981 was determined by matching the study cohort to the Israel Cancer Registry. The observed number of cancers was compared with sex-age-ethnic and calendar-year, site-specific national cancer rates. There were 42 cancers observed compared with 37.4 expected, yielding a standardized incidence ratio of 1.1 (95% confidence interval (CI) = 0.8-1.5). Analysis by infertility diagnosis demonstrated no significant excess of total cancer incidence; the standardized incidence ratio was 1.3 (95% CI = 0.8-1.8) for infertility due to hormonal deficiency, 0.7 (95% CI = 0.3-1.4) for mechanical infertility, 1.6 (95% CI = 0.6-3.6) for infertility of the male partner, and 1.1 (95% CI = 0.5-2.2) for unclassified diagnosis. Site-specific analyses revealed a significantly increased risk (8.0; 95% CI = 2.5-19.3; four cases observed, 0.50 expected) of endometrial cancer for the hormonal group and a nonsignificant excess of breast cancer and melanoma. Although numbers were small, women with disorders causing unopposed estrogen production had a risk of 1.4 (95% CI = 0.8-2.2) for all cancer sites, which reached 10.3 (95% CI = 2.6-28.2; three cases observed, 0.29 expected) for endometrial cancer and 1.8 (95% CI = 0.8-3.4; eight cases observed, 4.43 expected) for breast cancer. Among women with nonhormonal infertility, there was a suggestion of increased risks of carcinoma of the ovary (3.2; 95% CI = 0.3-32.9; two cases observed, 0.63 expected) and thyroid (3.0; 95% CI = 0.3-24.6; two cases observed; 0.67 expected). No evidence of an association between ovulation-inducing drugs and cancer was found. This study supports the hypothesis that infertility caused by hormone deficiency is a risk factor for uterine cancer, but is inconclusive regarding breast cancer.     

Second malignancies following conventional or combined 252Cf neutron brachytherapy with external beam radiotherapy for breast cancer

We retrospectively evaluated the risk of second malignancies among 832 patients with inner or central breast cancer treated with conventional external beam schedule (CRT group), or neutron brachytherapy using Californium-252 (²⁵²Cf) sources and hypofractionated external beam radiotherapy (HRTC group), between 1987 and 1996 at the Institute of Oncology, Vilnius University. Patients were observed until the occurrences of death or development of a second malignancy, or until 31 December 2009, whichever was earlier. Median follow-up time was 10.4 years (range, 1.2–24.1 years). Risk of second primary cancers was quantified using standardized incidence ratios (SIRs). Cox proportional hazards regression models were used to estimate hazard ratios (HRs). There was a significant increase in the risk of second primary cancers compared with the general population (SIR 1.3, 95% CI 1.1–1.5). The observed number of second primary cancers was also higher than expected for breast (SIR 1.8, 95% CI 1.3–2.4) and lung cancer (SIR 3.8, 95% CI 2.0–6.7). For second breast cancer, no raised relative risk was observed during the period ≥10 or more years after radiotherapy. Compared with the CRT group, HRTC patients had a not statistically significant higher risk of breast cancer. Increased relative risks were observed specifically for age at initial diagnosis of <50 years (HR 2.9, 95% CI 1.6–5.2) and for obesity (HR 2.8, 95% CI 1.1–7.2).     

Cancer incidence among priests: 45?years of follow-up in four Nordic countries

Previously published studies on the risk of cancer among male priests have been based on cancer mortality with the exception of one case–control study. The aim of this study was to present estimates of cancer incidence among Nordic male priests. The study cohort for our analyses consisted of 6.5 million men aged 30–64 years old who had participated in any computerised population census in four Nordic countries in 1990 or earlier. Follow-up was done by drawing linkages with the national population and cancer registries. 13,491 priests were identified by their job title codes. We estimated the standardised incidence ratio (SIR) and 95% confidence intervals (95% CI) for the priests using the male population as a reference. Priests had a lower cancer incidence than the general population (overall SIR 0.85, 95% CI: 0.82–0.88). The majority of smoking- and alcohol-related cancers were associated with decreased SIR estimates. Increased risks were observed for skin melanoma (SIR 1.34, 95% CI: 1.11–1.62), acute myeloid leukemia (SIR 1.75, 95% CI: 1.20–2.47) and thyroid cancer (SIR 1.86, 95% CI: 1.22–2.73). This is the first cohort study regarding the incidence of cancer among priests. The lower incidence of smoking and alcohol-related cancers among Nordic male priests can be explained by their lower exposure to cigarettes and alcohol when compared to the general population. A greater risk of melanoma is typical of highly-educated people, but it is unclear why priests should have an increased risk of acute myeloid leukemia or thyroid cancer.     

High folate intake is associated with lower breast cancer incidence in postmenopausal women in the Malmö Diet and Cancer cohort

BACKGROUND: Epidemiologic studies of associations between folate intake and breast cancer are inconclusive, but folate and other plant food nutrients appear protective in women at elevated risk. OBJECTIVE: The objective was to examine the association between folate intake and the incidence of postmenopausal breast cancer. DESIGN: This prospective study included all women aged >or=50 y (n = 11699) from the Malm? Diet and Cancer cohort. The mean follow-up time was 9.5 y. We used a modified diet-history method to collect nutrient intake data. At the end of follow-up, 392 incident invasive breast cancer cases were verified. We used proportional hazard regression to calculate hazard ratios (HRs). RESULTS: Compared with the lowest quintile, the incidence of invasive breast cancer was reduced in the highest quintile of dietary folate intake (HR: 0.56; 95% CI: 0.35, 0.90; P for trend = 0.02); total folate intake, including supplements (HR: 0.56; 95% CI: 0.34, 0.91; P for trend = 0.006); and dietary folate equivalents (HR: 0.59; 95% CI: 0.36, 0.97; P for trend = 0.01). CONCLUSION: A high folate intake was associated with a lower incidence of postmenopausal breast cancer in this cohort.