N. S. Weiss

Progestagen supplementation of exogenous oestrogens and risk of endometrial cancer

The favourable effects of exogenous progestagen on the endometrium are well known, but have not been adequately quantified with respect to endometrial cancer. The benefits of progestagen need to be weighted against its possible untoward effects on the risk of breast cancer and cardiovascular disease. A population-based case-control study of endometrial cancer was undertaken to evaluate the benefits of progestagen use. 158 incident cases were identified between 1985 and 1987 among women aged 40-64 years who were residents of King County, Washington. Detailed interviews were conducted and the responses were compared with those of 182 controls selected by random telephone digit dialling. The risk of endometrial cancer among women who had used unopposed oestrogen for more than 3 years was over five times that of women who had used no hormones (relative risk [RR] 5.7, 95% confidence interval [Cl] 2.5-12.8), whereas those who had also used a progestagen for at least six months of that time had an RR of only 1.6 (95% Cl 0.6-3.9). The RR differed according to days per month that progestagen was used: 2.4 (0.6-9.3) for progestagen use of less than 10 days per month versus 1.1 (0.4-3.6) for use of 10 or more days per month. These results provide additional evidence that the use of progestagen for 10 or more days per cycle can reduce the excess risk of endometrial cancer associated with long-term postmenopausal oestrogen use.

Surveillance of nasal and bladder cancer to locate sources of exposure to occupational carcinogens.

OBJECTIVE: To locate sources of occupational exposure to nasal and bladder carcinogens for surveillance follow up in British Columbia, Canada. METHODS: Incident cases of nasal cancer (n = 48), bladder cancer (n = 105), and population based controls (n = 159) matched for sex and age, were interviewed about their jobs, exposures, and smoking histories. Odds ratios (ORs) were calculated for 57 occupational groups with stratified exact methods to control for age, sex, and smoking. RESULTS: Occupational groups at increased risk of nasal cancer included: textile workers (six cases, OR 7.6); miners, drillers, and blasters (six cases, OR 3.5); welders (two cases, OR 3.5); pulp and paper workers (three cases, OR 3.1); and plumbers and pipefitters (two cases, OR 3.0). Nasal cancer ORs were not increased in occupations exposed to wood dust, possibly due to low exposures in local wood industries. Strongly increased risks of bladder cancer were found for sheet metal workers (four cases, OR 5.3), miners (19 cases, OR 4.5), gardeners (six cases, OR 3.7), and hairdressers (three cases, OR 3.2). Among occupations originally considered at risk, the following had increased risks of bladder cancer: painters (four cases, OR 2.8); laundry workers (five cases, OR 2.3); chemical and petroleum workers (15 cases, OR 1.8); machinists (eight cases, OR 1.6); and textile workers (three cases, OR 1.5). CONCLUSIONS: Occupational groups with increased risks and three or more cases with similar duties were selected for surveillance follow up. For nasal cancer, these included textile workers (five were garment makers) and pulp and paper workers (three performed maintenance tasks likely to entail stainless steel welding). For bladder cancer, these included miners (12 worked underground), machinists (five worked in traditional machining), hairdressers (three had applied hair dyes), and laundry workers (three were drycleaners).

Risk of cutaneous melanoma in a cohort of infertile women.

We assessed the risk of cutaneous malignant melanoma associated with the presence of ovulatory abnormalities and with the use of ovulation-inducing agents (such as clomiphene citrate) in a cohort of 3,837 women evaluated at infertility clinics in Seattle, WA, between 1974 and 1985. Computer linkage with a population-based tumour registry was used to identify women diagnosed with melanoma before 1992. Data regarding infertility testing and treatment were abstracted from the infertility clinic medical records for women who developed cancer and a randomly selected subcohort. Twelve women in the cohort developed cutaneous malignant melanoma, in comparison with an expected number of 6.8 cases (standardized incidence ratio = 1.8; 95% confidence interval (CI) 0.9–3.1). Within the cohort, risk was increased among women who had used clomiphene during 12 or more menstrual cycles (relative risk = 2.2; 95% CI 0.5–10.2). All four of the women with this duration of clomiphene use who developed melanoma had ovulatory abnormalities, and three had also used human chorionic gonadotropin (HCG). No elevation in risk associated with the presence of ovulatory abnormalities was observed in the absence of at least 12 cycles of clomiphene exposure; also, there was no increased risk associated with long-term use of clomiphene among women without ovulatory abnormalities, but the number of such women was very small. Thus, it is not certain to what extent the observed increased risk of melanoma in this cohort (if not due to chance) may be attributable to the use of clomiphene or HCG, or is a reflection of some underlying hormonal abnormality for which the drug was administered.