Abstract
BACKGROUND: Primary pure mucinous adenocarcinoma (PMA) is a rare type of lung cancer with unique clinical and prognostic features. Previous studies have shown that PMA have more early-stage cancer compared with other adenocarcinoma (ADC) subtypes. The clinicopathological features and optimal treatment strategies of resectable locally advanced mucinous adenocarcinoma lack evidence and require further study. METHODS: In this study, we collected information from patients with stage III-N2 PMA who underwent radical surgery between 2004 and 2016 from the Surveillance, Epidemiology, and End Results (SEER) database. The clinicopathological parameters, treatments, overall survival (OS), and cancer-specific survival (CSS) were evaluated. RESULTS: Of 242,699 eligible lung adenocarcinoma patients, 124 with PMA and 3405 with other ADCs of stage III-N2 received radical surgery were identified. Compared with other ADCs, PMA tended to appear more in the lower lobes, with higher degree of differentiation, less early T stage, and more positive lymph nodes numbers. Patients with PMA had significantly worse survival than other ADCs (OS = 45.0 vs. 57.1 months, p = 0.005, CSS = 51.8 vs. 65.5 months, p = 0.017). We explored the benefit population of postoperative radiotherapy (PORT) and found that the population with ≤7 positive lymph nodes could benefit from PORT, and OS was significantly improved (41.2 vs. 69.3 months, p = 0.034). For patients with >7 positive lymph nodes, PORT did not provide a survival benefit, while chemotherapy improved OS (10.9 vs. 23.3 months, p = 0.041). Multivariate analysis showed that race, tumor location, number of positive lymph nodes, and PORT were independent prognostic factors in patients with postoperative III-N2 lung PMA. CONCLUSION: The prognosis of patients with resectable III-N2 primary lung PMA was significantly worse than that of other ADCs, and PORT was an independent prognostic factor. Patients with ≤7 positive lymph nodes could benefit from PORT and those with >7 positive lymph nodes could benefit from chemotherapy.