Second primary lung cancers among breast cancer patients treated with anti-estrogens have a longer cancer-specific survival

Estrogen is thought to play an important role in lung cancer carcinogenesis and progression. The incidence and survival of second primary lung cancer among breast cancer patients with and without anti-estrogen therapy were evaluated. All women diagnosed with breast cancer and treated at the Sun Yat-Sen Cancer Center between January 2000 and December 2009 were included and followed-up for occurrence and/or death from lung cancer until December 2011. Twenty-six women developed second primary lung cancer among 6,361 breast cancer patients. All but one were adenocarcinoma and none had a smoking habit. Seventeen (65.4%) patients had previously received anti-estrogen treatment. The relative risk of developing second primary lung cancer among those who have received anti-estrogens for breast cancer and those who have not was 1.01 (95% confidence interval (CI)=0.45~2.28; p=0.970). Second primary lung cancer patients who have received anti-estrogens had a longer cancer-specific survival (p=0.007). The multivariate Cox proportional hazards analysis showed that anti-estrogen therapy remained an independent prognostic factor with a hazard ratio of 0.11 (95% CI=0.01~0.97, p=0.002) for second primary lung cancer patients. The results of this study further support the fact that estrogen adversely affects the prognosis of patients with lung cancer. However, the role of estrogen in lung cancer carcinogenesis remains to be determined.