Characteristics of menstruation and pregnancy and the risk of lung cancer in women.

Lung tissue, both normal and cancerous, has been found to express estrogen receptors and patterns of expression have differed between men and women, suggesting a possible role for hormone-related factors in lung carcinogenesis in women. Few epidemiological studies have examined hormone-related variables and lung cancer risk and the findings have not been consistent. We investigated the association between characteristics of menstruation and pregnancy in relation to lung cancer risk in a population-based case-control study carried out in Montreal, Canada, including 422 women with lung cancer and 577 controls. For each variable, odds ratios (OR) and 95% confidence intervals (CI) were estimated using unconditional logistic regression modeling. Associations were also examined according to level of smoking and by lung cancer histology. All statistical tests were two-sided. Most characteristics of menstruation and pregnancy were not associated with lung cancer risk. However, an increased risk was observed for women who had had a non-natural menopause, which predominantly included women who had had a bilateral oophorectomy, compared with women who had had a natural menopause (OR = 1.92, 95% CI: 1.22-3.01). An inverse association with age at menopause was suggested. These results did not vary by level of smoking and they were similar for adenocarcinomas compared with other histological types. Our results suggest that hormonal factors, related to early menopause and/or ovary removal, may play a role in the risk of lung cancer. Further studies are needed to confirm these findings, and to assess the possible contribution of hormone replacement therapy.