A prospective study of reproductive factors, hormone use, and risk of lung cancer in postmenopausal women

Abstract

1501 Background: There has been increased interest in understanding the role of hormonal factors in lung cancer (LC) in women with the observation that it exhibits different epidemiologic patterns and treatment response when compared to men. However, results of published studies have been inconsistent, possibly due to inadequate smoking adjustment. Methods: We prospectively examined the associations between reproductive factors, exogenous hormone use, and LC incidence in 106,574 postmenopausal women in the Nurses’ Health Study. Participants completed biennial questionnaires which included updated smoking history. We assessed age at menopause, age at menarche, type of menopause, parity, postmenopausal hormone (PMH), and oral contraceptive use. Cox proportional hazards modeling was used to estimate the relative risks (RR) of each exposure, adjusted for smoking status, number of cigarettes, time since quitting, age of initiating smoking, fruit/vegetable intake, body mass index, and environmental smoking exposure. Results: We identified 1,565 LC cases during follow up from 1984 to 2004. Parity was associated with decreased LC risk in never smokers (RR = 0.54, 95% CI 0.31–0.96) but increased risk in current smokers (RR = 1.44, 95% CI 1.03–2.02). No association was seen in former smokers. Also, younger age at menopause was associated with higher LC risk in women with natural menopause (p-trend = 0.016). PMH use was not associated with LC incidence. The RR for current PMH users was 1.01 (95% CI 0.87–1.17) and for past users was 0.95 (95% CI 0.82–1.1). No significant association was seen when assessed by duration of PMH use, time since last use, or type of PMH. However, past use of oral contraceptives for greater than 5 years was associated with increased LC risk (RR = 1.2, 95% CI 1.03–1.41). Conclusions: These results suggest that there may be an association between hormonal factors and LC development, and further suggest that the mechanism may differ in smokers versus lifelong never smokers. No significant financial relationships to disclose.