Lung cancer accounts for the most cancer-related deaths in the world. Our previous study suggested the improved survival of lung cancer patients, mainly female patients, with subsequent metachronous primary breast cancer. However, whether the survival advantages of the two primaries are associated with patients' sex and the specific breast cancer is unclear. Whether male lung cancer patients with another primary may encounter the same survival advantage as female patients is also uncertain. The uncertainty hinders these patients from the potential benefit of lung cancer clinical trial. A total of 343 male lung adenocarcinoma patients with subsequent bladder papillary transitional cell carcinoma (LCBC), 1539 lung adenocarcinoma patients with prior bladder papillary transitional cell carcinoma (BCLC), 1181 lung adenocarcinoma patients with subsequent prostate adenocarcinoma (LCPC), 7426 lung adenocarcinoma patients with prior prostate adenocarcinoma (PCLC), and patients with single bladder/prostate/lung (SLC) cancer were identified from the Surveillance, Epidemiology, and End Results. Patients were classified into simultaneous two primary cancer (sTPC), metachronous two primary cancer 1 (mTPC1), or mTPC2 groups when interval time between two cancers was within 6 months, between 7 and 60 months, or over 60 months, respectively. Propensity matching score program was executed to match the two primary cancers with single primary. Cox regression and competing risk regression were performed to identify confounders associated with all-cause and cancer-specific survival, respectively. The major cancer-related and non-cancer-related death in the two primaries were lung cancer and heart disease, respectively. Median overall survival times since lung primary of LCBC and SLC were 97 and 17 months, respectively, and incidence of all-cause and cancer-specific death in LCBC since lung malignancy was significantly lower (Coef. - 1.24, 95% CI - 1.49 to 0.99; SHR 0.42, 95% CI 0.33-0.53). Among the categorized groups, prognosis values of sTPC and mTPC2 groups were not statically different from that of the matched single lung cancer, whereas increased overall survival time and decreased incidence of all-cause and cancer-specific death relative to the matched patients were observed in mTPC1 group (H.R 0.28, 95% CI 0.19-0.41; SHR 0.33, 95% CI 0.23-0.47). Similar prognosis of LCPC relative to SLC was also observed. Furthermore, a generally improved survival relative to SLC was observed in PCLC (median survival times of PCLC and SLC were 17 and 12 months, respectively; Coef. - 0.32, 95% CI - 0.43 to 0.22; SHR 0.77, 95% CI 0.69-0.85), whereas prognosis of BCLC was similar to the matched ones. These results hinted that survival of lung cancer patients might vary with prior cancer history. Further analysis among groups with the two primaries suggested that advanced bladder cancer was not associated with prognosis of patients with LCBC and BCLC. On the contrary, advanced prostate cancer was associated with all-cause and cancer-specific death in patients with PCLC but not in patients with LCPC. Compared with patients with single lung cancer, male lung cancer patients with subsequent bladder/prostate primary over 6 months experienced generally improved survival. These results were similar to our previous study regarding female lung cancer patients with another breast primary. On the contrary, male lung cancer patients with prior primary malignancy encountered varied prognosis: improved survival relative to single lung primary was observed in lung cancer with prior prostate cancer, whereas prognosis of lung cancer with prior bladder cancer was not different. Therefore, great attention was required to characterize prognosis of lung cancer patients with another primary in advance, which was essential to eliminate the potential bias when these patients were included into the clinical trials.
© 2023. The Author(s).