Interstitial pneumonia caused by Photoimmunotherapy with cetuximab-IR700 conjugate

Photoimmunotherapy (PIT) is a newly developed cancer therapy that uses the tumor-targeted monoclonal antibody cetuximab conjugated to the photoabsorbing dye IR700. It is currently approved for the treatment of unresectable, locally advanced, or locoregionally recurrent head and neck cancers in Japan. However, data regarding the clinical safety of PIT are currently limited in the literature. Herein, we report the case of a 70-year-old man with nasopharyngeal squamous cell carcinoma who developed interstitial pneumonia after receiving PIT. He developed a fever 3 days after PIT, and computed tomography revealed ground-glass opacities in both lungs. He was diagnosed with drug-induced interstitial pneumonia, and subsequently responded well to prednisolone therapy. This case highlights the potential risk of interstitial pneumonia associated with the cetuximab-IR700 conjugate used in PIT. Clinicians should consider the possibility of interstitial lung disease whenever fever persists following PIT. Further studies are warranted to fully characterize the safety profile of PIT.