346 - Differential Survival Benefits of PORT in AJCC-9th /IASLC-Defined N2 NSCLC Substages: A Multicenter Real-World Study

04:00pm - 04:10pm PT

Room 155/157

Presenter(s)

Yongxing Bao, MD - National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, CAMS & PUMC, Beijing, Beijing

Y. Bao¹, Y. Lu², Y. Men¹, Z. Hui¹, and X. Cai²; ¹Department 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, ²Department of Radiation Oncology, Shanghai Chest Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China, Shanghai, China

Purpose/Objective(s): The phase III LungART and PORT-C trials demonstrated that postoperative radiotherapy (PORT) failed to confer survival benefits across all patients with N2-positive non-small cell lung cancer (NSCLC). Notably, the updated 9th edition AJCC staging system stratifies N2 disease into single-station (N2a) and multi-station (N2b) involvement. Furthermore, the International Association for the Study of Lung Cancer subclassifies N2 NSCLC into: single-station N2 without N1 involvement (N2a1) and single-station N2 with concurrent N1 involvement (N2a2). This multicenter study aimed to evaluate PORT efficacy according to these refined N2 descriptors.

Materials/Methods: This retrospective analysis from two tertiary cancer centers included patients with histologically confirmed pN2 NSCLC who underwent complete resection across. Participants were categorized into PORT and no-PORT cohorts. The primary endpoint was disease-free survival (DFS), with overall survival (OS) and locoregional recurrence-free survival (LRFS) as secondary endpoints.

Results: Among 3,122 eligible patients (N2a1: 551; N2a2: 1,064; N2b: 1,507) with a median follow-up of 49.1 months, distinct survival patterns emerged. For N2a1 patients, PORT showed no DFS benefit (median DFS PORT vs. no-PORT: 31.4 vs. 34.9 months, P = 0.91) or OS advantage (P = 0.45), though it significantly improved LRFS (median LRFS NR vs. 79.6 months, P = 0.01). In contrast, N2a2 patients receiving PORT demonstrated significant DFS (median DFS 26.4 vs. 21.5 months, P = 0.008), OS (P = 0.009), and LRFS (P < 0.001) improvements, results corroborated by multivariate analysis. Similarly, N2b patients benefited from PORT across all endpoints: DFS (median DFS 22.0 vs. 18.0 months, P = 0.01), OS (P < 0.001), and LRFS (P < 0.001).

Conclusion: PORT significantly improved survival outcomes in N2a2 and N2b NSCLC patients. Notably, N2a1 patients did not derive DFS or OS benefit from PORT despite improved locoregional control. These findings support tailored application of PORT based on refined nodal staging criteria.

Abstract 346 - Table 1: The survival outcomes of the PORT and no-PORT groups

	DFS (months)			OS (months)			LRFS (months)
	PORT	No-PORT	P value	PORT	No-PORT	P value	PORT	No-PORT	P value
N2a1	31.4	34.9	0.91	NR	91.9	0.45	NR	79.6	0.01
N2a2	26.4	21.5	0.008	87.9	58.7	0.009	103.5	50.0	<0.001
N2b	22.0	18.0	0.01	98.7	61.1	<0.001	86.7	43.3	<0.001