2010 - Efficacy of Postoperative Radiotherapy for Patients with 9th Stage N2 Descriptors in Completely Resected Non-Small Cell Lung Cancer: A Real-World Study

Y. Bao¹, Y. Men^1,2, X. Yang¹, S. Sun¹, Z. Ma¹, Y. Liu¹, J. Wang¹, L. Deng¹, W. Wang¹, Y. Zhai¹, N. BI¹, J. Lv¹, J. Liang¹, Q. Feng¹, D. Chen¹, Z. Xiao¹, Z. Zhou¹, L. H. Wang³, and Z. Hui^1,2; ¹Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, ²Department of VIP Medical Services, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, ³Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital & Shenzhen Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Shenzhen, China, Shenzhen, China

Purpose/Objective(s): The phase III LungART study and PORT-C study showed that postoperative radiotherapy (PORT) could not benefit all N2 patients with non-small cell lung cancer (NSCLC). The forthcoming 9^th AJCC stage divided the N2 stage into single station (N2a) and multi-stations (N2b). This study aimed to investigate the efficacy of PORT for patients with these N2 descriptors. Materials/

Methods: Patients with histologically confirmed pN2 NSCLC after complete resection were enrolled and divided into PORT and non-PORT groups. The primary endpoint was disease-free survival (DFS). The second endpoints were overall survival (OS) and locoregional recurrence-free survival (LRFS). Propensity-score matching (PSM) of baseline characteristics between the PORT and non-PORT groups was used for validation.
Results: A total of 1832 patients were enrolled, including 990 patients with N2a and 842 patients with N2b. The median follow-up time was 50.1 months. For patients with N2a, PORT significantly improved the DFS (median DFS 31.4 vs. 28.3 months, P=0.03) and LRFS (P=0.01) but did not improve the OS (P=0.11). The multivariate analysis and data after the PSM confirmed the benefits in DFS and LRFS, with no benefit observed in OS (multivariate analysis: HR 0.85; 95%CI, 0.63-1.13; P=0.26; median OS after PSM: 103.7 vs. 80.8 months, P=0.48). For patients with N2b, PORT could not improve the DFS (median DFS 20.6 vs. 21.2 months, P=0.39) but significantly improved the OS (P<0.001) and LRFS (P<0.001). The multivariate analysis showed that PORT significantly improved DFS (HR=0.81; 95%CI, 0.63-1.13; P=0.03), consistent with the data after the PSM (P=0.04).
Conclusion: PORT improved the DFS and LRFS in patients with N2a and the DFS, LRFS, and OS in patients with N2b. Patients with N2a might be further divided to distinguish the population who could not benefit from PORT.

Abstract 2010 - Table 1: The survival outcomes of the PORT and non-PORT groups before and after PSM

		DFS (months)			OS (months)			LRFS (months)
		PORT	Non-PORT	P value	PORT	Non-PORT	P value	PORT	Non-PORT	P value
N2a	Before PSM	31.4	28.3	0.03	103.7	81.2	0.11	103.5	55.1	0.01
	After PSM	31.4	28.0	0.03	103.7	80.8	0.48	103.5	51.4	0.045
N2b	Before PSM	20.6	21.2	0.39	129.0	69.7	<0.001	67.4	41.5	<0.001
	After PSM	20.6	15.7	0.04	129.0	72.0	0.04	76.7	36.8	<0.001