This phase Ib study was designed to assess the safety/tolerability and preliminary antitumor activity of neoadjuvant low-dose radiotherapy (LDRT) plus durvalumab and chemotherapy for potentially resectable stage III non-small-cell lung cancer (NSCLC).Eligible patients received dose-escalated radiotherapy (10 Gy in 5 fractions [cohort 1], 20 Gy in 10 fractions [cohort 2], and 30 Gy in 15 fractions [cohort 3]) according to a 3 + 3 design, with concurrent durvalumab plus standard chemotherapy for two cycles. Primary objective was safety/tolerability. Secondary objectives included major pathological response (MPR), pathological complete response (pCR), event-free survival (EFS), and exploratory biomarker analysis.Nine patients were enrolled and completed the planned neoadjuvant therapy. No dose-limiting toxicity was recorded. Grade 3-4 treatment-related adverse events were observed in three (33.3 %) patients. Seven (77.8 %) patients successfully converted to resectable cases with R0 resection. No treatment-related surgical delay or death was reported. The MPR and pCR rates were both 33.3 % % (1/3) for cohort 1, 66.7 % (2/3) and 0.0 % for cohort 2, and 100.0 % (3/3), and 66.7 % (2/3) for cohort 3. At data cutoff, the 12 month-EFS rates were 33.3 %, 66.7 %, and 100 % for three cohorts, respectively. By biomarker analysis, TMB values were higher in either pathologically or radiologically responders than in others (all p > 0.05).Neoadjuvant LDRT plus durvalumab and chemotherapy was well-tolerated in potentially resectable stage III NSCLC. The preliminary efficacy supports this combined regimen's potential, the optimal radiotherapy dosage was determined to be 30 Gy in 15 fractions, warranting further clinical investigation.Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.