Prognostic Characteristics of Operated Breast Cancer Patients with Second Primary Lung Cancer: A Retrospective Study

BACKGROUND AND PURPOSE: The number of breast cancer patients with second primary lung cancer is increasing year by year. The aim of this study was to explore the prognostic characteristics of these multiple primary breast and lung cancer patients. METHODS: Operated breast cancer patients with subsequent lung cancer who were admitted to our hospital from January, 2010 to August, 2020 were retrospectively analyzed. The univariate and multivariate Cox regression analyses were conducted to explore the prognostic risk factors of such patients. Meanwhile, the propensity score match (PSM) method was applied to compare the prognosis between lung cancer patients with and without the history of breast cancer. RESULTS: A total of 137 cases were included and most of them (94.9%) were asynchronous multiple primary carcinomas. The median interval between the diagnoses of breast cancer and lung cancer was 60 months (2–456 months), median age at the diagnosis of breast cancer was 49.5 (28–81) years old and median age at the diagnosis of lung cancer was 58 (31–84) years old. Univariate and multivariate Cox regression analysis indicated that poor differentiation [hazard ratio (HR)=6.372, 95% confidence interval (CI): 2.441–16.633, P<0.001] and pTNM stage III/IV (HR=5.830, 95% CI: 2.295–14.813, P<0.001) of lung cancer were independent prognostic risk factors for these patients. Before and after the PSM, the overall survival (OS) of lung cancer patients with breast cancer was significantly worse than that of single primary lung cancer patients (P<0.001, P=0.002). CONCLUSION: Differentiation status and pTNM stage were independent prognostic factors in operated breast cancer patients with second primary lung cancer. Meanwhile, the prognosis of this group of patients was worse than single primary lung cancer patients, which indicated that the medical history of breast cancer was also a prognostic risk factor of female lung cancer patients.