Lattice-Based Radiotherapy and Chemoimmunotherapy for Oropharyngeal Squamous Cell Carcinoma

This single-arm Phase I/II trial evaluates induction chemoimmunotherapy combined with lattice radiotherapy (LRT) in patients with non-low risk oropharyngeal squamous cell carcinoma and primary tumor ≥3 cm or primary tumor and pathologic lymph node ≥3 cm in longest dimension. BOIN12 adaptive dose-finding will guide dose across two anatomical cohorts-primary-tumor only (P) and primary + largest involved node (PN)-with a total target accrual of about 60 evaluable patients. Dose-limiting toxicity is monitored separately in each cohort. If both tolerate the same dose, that unified optimal biological dose (OBD) advances to Phase II; if tolerability differs, the PN-specific OBD expands while the P cohort is analyzed descriptively. After induction, imaging determines response: patients achieving ≥50% volumetric tumor shrinkage receive hypofractionated chemoradiation, whereas those with \<50% shrinkage are treated with conventional fractionation, personalizing definitive therapy according to early safety and efficacy signals.