Impact of lymph node characteristics on clinical outcomes in clinical N2 non-small cell lung cancer patients treated with chemoradiotherapy: Single- vs. multiple-stations, bulky vs. non-bulky and discrete vs. infiltrative.

8051 Background: Stage III, N2 non-small cell lung cancer (NSCLC) is a heterogeneous disease with various patterns of lymph node metastasis. Recently, chemoradiotherapy followed by immune-checkpoint inhibitors (ICIs) and neoadjuvant chemotherapy with ICIs followed by surgery have been developed as treatment strategies for clinical N2 (cN2) NSCLC. However, the difference of clinical outcomes according to cN2 subclassification, such as single- vs. multiple-stations, non-bulky vs. bulky and discrete vs. infiltrative, in NSCLC patients treated with chemoradiotherapy are still unclear. Methods: The clinical outcomes in cN2 NSCLC patients who received chemoradiotherapy at our institution were retrospectively investigated and compared according to cN2 subclassification; single- vs. multiple-stations, non-bulky vs. bulky (short-axis diameter≧2cm) and discrete vs. infiltrative. Results: A total of 146 cN2M0 NSCLC patients received chemoradiotherapy from May 2018 to December 2023, and 98 (67%) patients received durvalumab after chemoradiotherapy. As of January 2025, the median follow-up was 20.9 months. The characteristics of the patients were showed that the median age was 71 (range 40-88) year-old, 77% were male, 89% had smoking history, 99% were ECOG PS 0-1, 44% had histology of adenocarcinoma and 23% were PD-L1 (22C3) ≥50%. Among them, 69 patients (47%) had single-station N2, 90 patients (62%) had non-bulky N2, and 81 patients (55%) had discrete N2. There was no significant difference of the progression-free survival (PFS) in the patients who received chemoradiotherapy between single- vs. multiple-stations (median: 17.5 vs. 12.5 months, HR [95%CI]: 0.90 [0.60–1.37], P = 0.63), non-bulky vs. bulky (median: 15.6 vs. 12.3 months, HR [95%CI]: 0.98 [0.64–1.50], P = 0.92), and discrete vs. infiltrative (median: 18.2 vs. 12.0 months, HR [95%CI]: 0.72 [0.47–1.08], P = 0.11). Similarly, there was no significant difference in the overall survival (OS) in the patients who received chemoradiotherapy between single- vs. multiple-stations (median: NR vs. NR months, HR [95%CI]: 1.01 [0.59–1.72], P = 0.97), non-bulky vs. bulky (median: 51.4 vs. NR months, HR [95%CI]: 1.06 [0.61–1.84], P = 0.84), and discrete vs. infiltrative (median: 51.4 vs. NR months, HR [95%CI]: 0.89 [0.52–1.52], P = 0.67). In the patients who received durvalumab after chemoradiotherapy, there was no significant difference in the PFS and OS according to cN2 subclassification. The time to recurrence in the radiated field showed no significant difference between single- vs. multiple-stations, non-bulky vs. bulky and discrete vs. infiltrative. Conclusions: Lymph node characteristics have no impact on clinical outcomes in cN2M0 NSCLC patients treated with chemoradiotherapy.