Predictive Factors for the Efficacy of Head and Neck Photoimmunotherapy and Optimization of Treatment Schedules.

Background/Aim: Head and neck photoimmunotherapy (HN-PIT) is a promising treatment for unresectable locally advanced or recurrent head and neck cancers. However, the optimal tumor characteristics and treatment schedules remain unclear. This study aimed to identify factors associated with treatment efficacy and assess the effectiveness of treatment schedules. Patients and Methods: A retrospective cohort study of patients treated with HN-PIT at Aichi Cancer Center Hospital from January 2021 to October 2024 was conducted. Tumor characteristics, treatment cycles, and outcomes were analyzed. The thickness and longest diameter of the tumors were evaluated, and treatment intervals were assessed for their association with complete response (CR). Results: Among the 19 patients (30 cycles), CR was observed exclusively in local lesions. Smaller and thinner lesions showed significantly better treatment responses. Thinner lesions were more likely to achieve CR after a single cycle, whereas intermediate-thickness tumors often required multiple cycles with shorter intervals. The regional lesions did not achieve CR, even with multiple cycles and shorter intervals. Age was a significant factor influencing CR. Conclusion: HN-PIT demonstrated promising efficacy for local lesions, particularly for smaller and thinner lesions. Optimizing treatment schedules, including shorter intervals for intermediate lesions, is critical for improving outcomes. Further research is needed to enhance the efficacy for regional lesions and refine treatment schedules.