Quad Shot Radiotherapy Combined With Tislelizumab and Platinum-Based Chemotherapy Before Surgery for Stage II-III Non-Small Cell Lung Cancer

Background: Neoadjuvant immune checkpoint inhibitor (ICI) combined with platinum-based chemotherapy has become a standard of care for resectable stage II-III NSCLC, as demonstrated by phase III trials such as CheckMate-816, KEYNOTE-671, and RATIONALE-315. However, a significant proportion of patients still fail to achieve deep pathological responses due to mechanisms such as poor antigen release, impaired antigen presentation, and an immunosuppressive tumor microenvironment (TME). Radiotherapy possesses immunomodulatory properties, inducing immunogenic cell death and promoting antigen release. However, traditional continuous fractionated radiotherapy may deplete circulating lymphocytes and cause normal tissue damage. The "Quad Shot" (QS) regimen is a cyclical hypofractionated radiotherapy approach (14-14.8 Gy in 4 fractions over 2 days) that has shown low toxicity in palliative settings. Its cyclical, pulsatile nature may provide repeated immune stimulation and TME remodeling, making it a promising partner for immunotherapy. Study Design: This is a single-arm, prospective, exploratory phase II clinical study. Patients with histologically or cytologically confirmed, untreated, resectable stage II-IIIB NSCLC (including T3-4N2 IIIB, AJCC 9th edition) will be enrolled. Patients will receive 3 cycles of neoadjuvant treatment (every 3 weeks): Quad Shot radiotherapy (14-14.8 Gy/4 fractions, Day 1-2) Tislelizumab (200 mg, Day 3) Platinum-based doublet chemotherapy (Day 3): Carboplatin (AUC 5) or Cisplatin (75 mg/m²) combined with Pemetrexed (500 mg/m², for non-squamous) or Paclitaxel (175 mg/m², for squamous). Following 3 cycles of neoadjuvant therapy, patients will undergo surgery 4-6 weeks (±7 days) after the last dose. Postoperative adjuvant therapy will be administered at the investigator's discretion according to NCCN and CSCO guidelines. Objectives and Endpoints: The primary objective is to evaluate the antitumor efficacy of this regimen, with the primary endpoint being the pathological complete response (pCR) rate. Secondary endpoints include major pathological response (MPR) rate, R0 resection rate, objective response rate (ORR) per RECIST v1.1, event-free survival (EFS), overall survival (OS), safety (NCI CTCAE v5.0), feasibility, surgical complications (Clavien-Dindo classification), and QS radiotherapy-related toxicities. Sample Size: A total of 12 patients will be enrolled, with at least 10 evaluable patients included in the primary endpoint analysis to account for an estimated 2 dropouts. Study Duration: The estimated enrollment period is 6-12 months, with an anticipated study completion date of December 2031.