Therapeutic Host Anticancer Immune Response through Photoimmunotherapy for Head and Neck Cancer May Overcome Resistance to Immune Checkpoint Inhibitors.

Introduction: Near-infrared photoimmunotherapy (NIR-PIT) is a recently developed hybrid cancer therapy that directly kills cancer cells while producing a therapeutic host anticancer immune response. The activation of host immunity using NIR-PIT can enhance the effects of immune checkpoint inhibitors (ICIs) in animal experimental models; however, there have been no reports of this phenomenon in humans. Furthermore, by activating host immunity using NIR-PIT in patients who have become resistant to ICIs, the effects of ICIs can be restored.

Case presentation: A 56-year-old male experienced local recurrence after chemoradiotherapy for maxillary sinus cancer (cT4bN0M0). The disease had progressed following ICI antiPD-1 antibody therapy. He underwent NIR-PIT for four cycles; however, a local recurrent tumor remained and began a rapid regrowth. The ICI antiPD-1 antibody was then readministered following NIR-PIT. As a result, sensitivity to antiPD-1 therapy was restored, and the tumor shrank. Finally, a complete response was observed without major adverse events associated with subsequent antiPD-1 antibody treatment following NIR-PIT.

Conclusion: These results indicated that NIR-PIT may not only activate host anticancer immunity but also enhance the effects of ICIs and overcome antiPD-1 resistance.