Lung cancer mortality risk among breast cancer patients treated with anti-estrogens

BACKGROUND: The Women's Health Initiative randomized clinical trial reported that menopausal hormone therapy increases lung cancer mortality risk. If this is true, use of anti-estrogens should be associated with decreased lung cancer mortality risk. The authors compared lung cancer incidence and mortality among breast cancer patients with and without anti-estrogen therapy.

METHODS: Our study included all 6655 women diagnosed with breast cancer between 1980 and 2003 and registered at the Geneva Cancer Registry. Among these women, 46% (3066) received anti-estrogens. All women were followed for occurrence and death from lung cancer until December 2007. The authors compared incidence and mortality rates among patients with and without anti-estrogens with those expected in the general population by Standardized Incidence Ratios (SIRs) and Standardized Mortality Ratios (SMRs).

RESULTS: After a total of 57,257 person-years, 40 women developed lung cancer. SIRs for lung cancer were not significantly decreased among breast cancer patients with and without anti-estrogens (0.63, 95% confidence intervals [CI], 0.33-1.10; and 1.12, 95% CI, 0.74-1.62, respectively) while SMR was decreased among women with anti-estrogens (0.13, 95% CI, 0.02-0.47, P<.001) but not for women without anti-estrogens (0.76, 95% CI, 0.43-1.23).

CONCLUSIONS: Compared with expected outcomes in the general population, breast cancer patients receiving anti-estrogen treatment for breast cancer had lower lung cancer mortality. This study further supports the hypothesis that estrogen therapy modifies lung cancer prognosis.