3669 - Definitive Radiotherapy with or without Concurrent Chemotherapy after Long-Course Induction Chemoimmunotherapy In Unresectable Stage III NSCLC
Presenter(s)
X. Chang1, H. Liang2, J. Xiao1, D. Yang1, J. Yu1, J. Shan1, D. Xin1, W. Deng1, Y. Zhao3, L. Jiang1, L. Liuhua1, Y. Teng1, H. Yu1, R. Yu1, S. Ma4, and A. Shi1; 1Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, Beijing, China, 2Oncology Department , The Second People's Hospital of Datong, Datong, China, 3Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education/Beijing), Department of Radiation Oncology, Peking University Cancer Hospital & Institute, China, Beijing, China, 4Key Laboratory of Molecular Oncology, Beijing Key Laboratory of Carcinogenesis and Translational Research, Department of Thoracic Surgery I, Peking University Cancer Hospital & Institute, Beijing, China
Materials/Methods:
We retrospectively analyzed 153 patients with unresectable stage III NSCLC treated at one institution from 2021 to 2024 who received =3 cycles of induction chemoimmunotherapy followed by definitive RT alone (n=63) or concurrent chemoradiotherapy (CRT; n=90), with or without consolidation immunotherapy. Definitive RT was delivered via IMRT or VMAT, typically 50.4–60 Gy in 28–30 fractions with a simultaneous boost to 60–66 Gy, with some patients receiving hypofractionation. CRT was administered with concurrent platinum-based doublet chemotherapy. Stable inverse probability of treatment weighting (sIPTW) was applied to balance baseline covariates (e.g., age, sex, ECOG performance status, histology, stage, PD-L1 status, induction regimen and response, and consolidation therapy). PFS, defined from the start of induction therapy to radiographic progression or death, was analyzed using Kaplan–Meier methods and Cox proportional hazards models to estimate hazard ratios (HRs) with 95% confidence intervals (CIs).Results:
At a median follow-up of 25.8 months, PFS was similar between RT and CRT (HR=0.83; 95% CI, 0.51–1.37; P=0.46) and remained comparable after sIPTW (HR=0.80; 95% CI, 0.47–1.35; P=0.46). Grade 3–4 hematologic adverse events (CTCAE v4.0) were more frequent with CRT than RT (24.4% vs 9.5%; P<0.001). In exploratory analyses, consolidation immunotherapy showed a numerical but non-significant PFS improvement (HR=0.78; 95% CI, 0.48–1.27; P=0.32).Conclusion:
After long-course induction chemoimmunotherapy for unresectable stage III NSCLC, adding concurrent chemotherapy to definitive RT did not improve PFS and led to more severe hematologic toxicity. Definitive RT alone may be a reasonable option for selected patients. Prospective studies are warranted to define the optimal definitive local therapy and consolidation strategies.