Survival Analysis of Secondary Primary Lung Cancer After Breast Cancer Patients: Insights From a Retrospective Single-Center Study of Clinical Outcomes and Prognostic Indicators.

BACKGROUND

Breast cancer (BC) and lung cancer are the two most common malignancies among women in China. As breast cancer diagnostic and therapeutic technologies continue to advance, the lifespan of patients with breast cancer has been extended, and the number of breast cancer patients with second primary lung cancer (SPLC) has increased. Furthermore, among women with SPLC, breast cancer stands as the most prevalent initial malignancy, and SPLC remains the predominant cause of mortality within this demographic. The aim of this retrospective study was to analyze the clinical characteristics of breast cancer with SPLC patients and to investigate postoperative survival and prognostic factors. This retrospective study analyzed 150 patients diagnosed with primary lung cancer in BC at one cancer center in China from January 2000 to December 2020.

METHODS

We assessed demographic data, cancer characteristics, treatment modalities, and survival outcomes. Survival curves were generated using the Kaplan-Meier method, and the significance of survival differences among selected variables was verified using the log-rank test. A univariate Cox regression analysis was used for estimating hazard ratios. A multivariate Cox regression analysis with a backward elimination method was used to estimate hazard ratios and to identify independent prognostic factors.

RESULTS

There were 29 cases (19.3%) of death. The median follow-up time for this cohort was 96.3 months. The median OS was calculated at 60.0 months, with survival rates at 1-, 3-, 5-, and 10-year marked at 89.7%, 65.5%, 44.8%, and 10.3%. The median time from BC surgical treatment to the occurrence of SPLC was observed at 4.5 months. A peak period of SPLC occurs in the first year after BC surgery. The median follow-up time from SPLC surgical treatment to death or the end of follow-up was 73.5 months. The median survival time from SPLC surgical treatment to death by any cause was 39.2 months, with survival rates at 1-, 3-, and 5-year marked at 86.2%, 51.7%, and 31.0%, and survival rates were 0% at the 9th year. The average age at BC diagnosis was 53.8 ± 10.4 years (range 25-81). 41.3% of patients had other chronic diseases. The average menarche age was 14.7 ± 1.5 years (range 11-20). 64.7% of patients had menopause. Independent prognostic factors for the BC with SPLC by multivariate analysis were the status of menopause and T-stage of SPLC.

CONCLUSIONS

Further analysis revealed that patients who were menopausal and had a poor T stage of SPLC had a higher mortality rate. Based on these findings, future studies should focus on the menstrual status, hormone levels, and pathological stage of SPLC in BC patients.