Prognostic study for survival outcome following the treatment of second primary lung cancer in patients with previously resected non‐small cell lung cancer

BACKGROUND: Patients who have previously undergone surgical resection of initial primary lung cancer (IPLC) are at high risk of developing second primary lung cancer (SPLC). There are still no standard treatments for SPLC. This study aimed to identify the prognostic factors and compare survival between the different SPLC treatment groups. METHODS: SPLC patients in the Surveillance, Epidemiology, and End Results (SEER) database between 2007 and 2016 were retrospectively reviewed. Prognostic factors for SPLC were identified, using the least absolute shrinkage and selection operator (LASSO) regression and univariate Cox analysis to select variables for multivariate Cox analysis. Kaplan‐Meier method plus log‐rank test and restricted mean survival time (RMST) were used to compare survival outcome. RESULTS: A total of 665 SPLC patients were finally enrolled into the study. Multivariate Cox regression analysis revealed that male vs. female (HR = 1.82, 95% CI: 1.29–2.59, P = 0.001), tumor size of SPLC ≥1 cm vs. <1 cm (HR = 1.80, 96% CI: 1.07–3.02, P = 1.028), IPLC characteristics of squamous cell carcinoma vs. adenocarcinoma (HR = 1.89, 95% CI: 1.17–3.04, P = 0.009), clinical stage II vs. stage I (HR = 2.60, 95% CI: 1.08–6.27, P = 0.033), and T2 stage vs. T1 stage (HR = 1.68, 95% CI: 1.04–2.72, P = 0.034) indicated worse survival. SPLC patients demonstrated a five‐year survival rate of 68.6% and a five‐year RMST of 49.4 months. The choice of surgical procedure (wedge resection, segmentectomy and lobectomy) for both IPLC and SPLC had no significant effect on prognosis (P > 0.05). Patients that received radiotherapy for SPLC also demonstrated similar survival when compared with those that underwent surgery (P > 0.05). CONCLUSIONS: Radiotherapy and sublobar resection can be considered reasonable alternative treatments for SPLC, especially when patients are unable to tolerate lobectomy.