Postoperative Radiotherapy can Improve the Disease-Free Survival of EGFR Wild Type Patients with pN2 NSCLC after Complete Resection and Adjuvant Chemotherapy

Abstract

<h3>Purpose/Objective(s)</h3> Recently published phase III trials showed that postoperative radiotherapy (PORT) did not improve the survival of patients with pN2 non-small-cell lung cancer (NSCLC) after complete resection. However, the effect of PORT for pN2 NSCLC with different EGFR status remains unclear. <h3>Materials/Methods</h3> From 2010 to 2019, consecutive patients with pN2 NSCLC after complete resection and adjuvant chemotherapy who had detection of EGFR status were retrospectively analyzed. PORT was administered using IMRT at 2 Gy per fraction up to 50 Gy over 5 weeks. Patients were categorized into 4 groups according to EGFR status and treatment: Group 1 (EGFR wild type with PORT), Group 2 (EGFR wild type without PORT), Group3 (EGFR-mutated with PORT), Group 4 (EGFR-mutated without PORT). The Kaplan-Meier method and log-rank test were used to evaluate the disease-free survival (DFS), overall survival (OS), locoregional relapse free survival (LRFS), and distant metastasis free survival (DMFS). <h3>Results</h3> Totally 575 patients were enrolled. 264 patients (45.9%) were EGFR wild type, including 96 with PORT and 168 without PORT. 311 patients (54.1%) were EGFR-mutated, including 109 with PORT and 202 without PORT. The median DFS was 28.4 months in Group 1 and 17.3 months in Group 2 (HR 0.70, 95% CI 0.52-0.96, p=0.032). The median OS was not reached in Group 1 and Group 2 (HR 0.75, 95%CI 0.46-1.21, p=0.263). LRFS was statistically higher in Group 1 than Group 2 (HR 0.64, 95%CI 0.43-0.96, p=0.041). However, no significant difference was shown in DMFS (HR 0.75, 95%CI 0.54-1.04, P=0.097). Group 3 and Group 4 showed median DFS of 20.2 months and 25.7 months (HR 1.113, 95% CI 0.84-1.53, p=0.402), respectively. The median OS was not reached in either Group 3 or Group 4 (HR 0.64, 95% CI 0.33-1.21, p=0.201). LRFS was not significantly different (HR 0.83, 95% CI 0.53-1.31, p=0.45) in Group3 vs Group4, neither was DMFS (HR 1.15, 95%CI 0.85-1.57, p=0.73). <h3>Conclusion</h3> For completely resected pN2 NSCLC, PORT can improve DFS and LRFS in EGFR wild type patients. However, PORT may not prolong survival in EGFR-mutated patients. Prospective randomized clinical trials are needed for validation.