Reduced Lung Cancer Mortality Risk among Breast Cancer Patients Treated with Anti-Estrogens.

Abstract Background: The Women Health Initiative study recently reported that women on hormone replacement therapy (HRT) were at increased risk of dying from lung cancer. If exposure to estrogens can worsen lung cancer outcome, we hypothesized that anti-estrogens may, on the contrary, improve its prognosis. We compared lung cancer incidence and mortality among breast cancer patients with and without anti-estrogen therapy.Methods: All 6715 patients recorded with a breast cancer in the population-based Geneva Cancer registry in the period 1980-2003 were included in the study. Forty-six percent of these women (3066) received anti-estrogen therapy (tamoxifen in large majority). Age, sex and year-specific population data were used to calculate standardised incidence ratios (SIRs) and standardised mortality ratios (SMRs), to compare the study population to the general female population of Geneva canton. For each woman we computed person-years at risk from the date of diagnosis of breast cancer to the date of diagnosis of invasive lung cancer cancer, date of death, date lost to follow-up, or end of the study period (December 31, 2007).Results: The cohort yielded a total of 57,100 person-years.During the study period we observed a total of 40 cases of metachronous lung cancers (diagnosed at least six months after the breast cancer). Compared with the general population, the risk of developing a lung cancer among women who received anti-estrogens was 0.63 (95% Confidence Intervals [CI]: 0.33-1.10) and among women without anti-estrogens was 1.12 (95% CI: 0.74-1.62). Lung cancer mortality rate was 31.44/100,000. The mortality rate were 9.23/100,000 for women with anti-estrogens and 44.97/100,000 for women without anti-estrogens.Compared to the general population the SMR for lung cancer was 0.13 (95% CI: 0.02-0.47) among women who took anti-estrogens (p<0.001), and 0.76 (95% CI: 0.43-1.23) among women who did not receive anti-estrogens.Discussion: Women who received anti-estrogens as breast cancer treatment have a significantly decreased risk of dying from lung cancer. This result further supports the role of estrogens in lung cancer prognosis and suggests that exposure to anti-estrogens may offer some protection against tumor mortality. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 35.