Reproductive factors and risk of lung cancer in female textile workers in Shanghai, China

Purpose: Hormonal factors may play a role in the development of lung cancer in women. This study examined the relationship between lung cancer and reproductive factors in a large cohort of women, most of whom never smoked (97 %). Methods: A cohort of 267,400 female textile workers in Shanghai, China, enrolled in a trial of breast self-examination provided information on reproductive history, demographical factors, and cigarette smoking at enrollment in 1989-91. The cohort was followed until July of 2000 for incidence of lung cancer; 824 cases were identified. Hazard ratios (HR) and 95 % confidence intervals (CI) associated with selected reproductive factors were calculated using Cox proportional hazards modeling, adjusting for smoking, age, and also parity when relevant. Results: Nulliparous women were at increased risk compared to parous women (HR = 1.33, 95 % CI 1.00-1.77). Women who had gone through menopause at baseline were at increased risk compared to women of the same age who were still menstruating. Risk was higher in women with a surgical menopause (HR = 1.64, 95 % CI 0.96-2.79) than in those with a natural menopause (HR = 1.35, 95 % CI 0.84-2.18), and risk was highest in those postmenopausal women with a hysterectomy and bilateral oophorectomy at baseline (HR = 1.39, 95 % CI 0.96-2.00), although the risk estimates were not statistically significant. Conclusions: These results support experimental data that demonstrate a biological role for hormones in lung carcinogenesis.