Abstract
BACKGROUND: The 8(th) edition of the American Joint Committee on Cancer staging system for lung cancer made major revisions to T staging, especially the size division of stage II/III patients. However, the value of tumor size in the postoperative prognosis of IIIA-N2 non-small cell lung cancer (NSCLC) is seldom mentioned, and survival data of such patients should be re-evaluated according to the 8(th) edition staging system. METHODS: Patients with IIIA-N2 NSCLC after surgery were identified in the Surveillance, Epidemiology, and End Results database (n=4,128). All patients were stratified according to tumor size, 5-year overall survival (OS) was then compared. Cox regression analysis was used to determine the value of size to discriminate patients with prognostic differences and establish a predictive nomogram system. Patients with IIIA-N2 NSCLC from our own institute (n=583) were used to validate the results. RESULTS: The prognosis of patients with tumor sizes of 0-2, 2-4 and 4-5 cm differed greatly from each other in the training cohort, with 5-year OS rates of 53.7%, 43.9% and 36.9% respectively (P<0.001), in the validation cohort, the rates were 54.1%, 38.4% and 33.8% respectively. Tumor size >2 cm was considered an independent risk factor compared to the ≤2 cm group in the Cox regression analysis: 2-4 cm (HR =1.25, 1.12-1.39; P<0.001), 4-5 cm (HR =1.51, 1.32-1.39; P<0.001), the validation cohort showed the same trend. The concordance index of the training set was 0.634 (0.622-0.646), while that of the validation set was 0.716 (0.686-0.746). The calibration plot showed optimal consistency between the nomogram predicted survival and observed survival. CONCLUSIONS: Tumors with different sizes showed significant postoperative survival differences among patients with IIIA-N2 NSCLC. Tumor size should be considered when making surgery decisions in such patients, with tumor size ≤2 cm showing considerably better prognosis.