Better survival and prognosis in SCLC survivors after combined second primary malignancies: A SEER database-based study

With recent advances in treatment modalities, the survival time for patients with small cell lung cancer (SCLC) has increased, along with the likelihood of recurrence of a second primary tumor. However, patient treatment options and prognosis remain uncertain. This research evaluated the survival rates of patients with SCLC with a second malignancy, aiming to provide new insights and statistics on whether to proceed with more active therapy. SCLC patients were selected based on the Surveillance, Epidemiology, and End Results (SEER) database, updated on April 15, 2021. We defined those with SCLC followed by other cancers (1st of 2 or more primaries) in the sequence number as S-second primary malignant cancer (S-SPM). Those who had other cancers followed by SCLC (2nd of 2 or more primaries) were defined as OC-SCLC. We performed Kaplan-Meier survival analysis, life table analysis, univariate analysis, stratified analysis, and multiple regression analysis of patient data. We considered the difference statistically meaningful at P < .05. After selection, data for 88,448 participants from the SEER database was included in our analysis. The mean survival time for patients with S-SPM was 69.349 months (95% confidence interval [CI]: 65.939, 72.759), and the medium duration of survival was 34 months (95% CI: 29.900, 38.100). Univariate analysis showed that for overall survival, the hazard ratio (HR) of S-SPM was 0.367 (95% CI: 0.351, 0.383), which was 0.633 lower than that of patients with solitary SCLC and 0.606 lower than that of patients with OC-SCLC. For cancer-specific survival (CSS), the HR of S-SPM was 0.285 (95% CI: 0.271, 0.301), which was 0.715 lower than for patients with solitary SCLC and 0.608 lower than that for patients with OC-SCLC. Multiple regression analysis showed that the HR values of S-SPM were lower than those of patients with single SCLC and those with OC-SCLC, before and after adjustment for variables. Kaplan-Meier survival curves showed that patients with S-SPM had significantly better survival times than the other groups. The survival time and prognosis of patients with S-SPM were clearly superior to those with single SCLC and OC-SCLC.