Fraction dose escalation of hypofractionated radiotherapy with concurrent chemotherapy and subsequent consolidation immunotherapy in locally advanced non-small cell lung cancer: a phase 1 study

Abstract Purpose: This phase 1 trial aimed to determine the maximum tolerated fraction dose (MTFD) of hypofractionated radiotherapy (hypo-RT) combined with concurrent chemotherapy and subsequent consolidation immune checkpoint inhibitors (cICI) for patients with locally advanced non-small cell lung cancer (LA-NSCLC). Patients and Methods: Split-course hypo-RT and hypo-boost combined with concurrent chemotherapy were administered at three dose levels (DLs), using a stepwise dose-escalation protocol. The sophisticated esophagus-sparing technique was implemented to restrict the dose to the esophagus. Patients who did not experience disease progression or unresolved G2+ toxicities after radiotherapy received cICI. Each DL aimed to treat 6 patients. The MTFD was defined as the highest DL at which <=2 patients of the 6 who were treated experienced treatment-related G3+ toxicity and <=1 patient experienced G4+ toxicity within 12 months post-radiotherapy. Results: Eighteen patients were enrolled with 6 patients in each DL. All patients completed hypo-RT and concurrent chemotherapy, and 16 (88.9%) received at least one infusion of cICI, with a median of 10 infusions. Within the 12-month assessment period, one patient in DL1 experienced G3 pneumonitis, and one patient in DL3 developed G3 tracheobronchitis. The MTFD was not reached. The objective response rate (ORR) was 100%. With a median follow-up of 20.9 months, the 1-year overall survival and progression-free survival rate were 94.4% and 83.3%, respectively. Conclusions: Utilizing the split-course hypo-RT and hypo-boost approach, a fraction dose of 5Gy to a total dose of 60Gy, combined with concurrent chemotherapy and subsequent cICI, was well-tolerated, and yielded promising ORR and survival outcomes.