Severe Checkpoint Inhibitor Pneumonitis and Lung Cancer Recurrence After Carbon-ion Radiotherapy in a Patient with Lung Squamous Cell Carcinoma.

Carbon-ion radiotherapy (CIRT) holds promise for central lung cancer owing to its non-invasiveness and precision. We report a case of lung squamous cell carcinoma treated with neoadjuvant chemoimmunotherapy followed by CIRT. The course was complicated by severe checkpoint inhibitor pneumonitis with concurrent Pneumocystis jirovecii pneumonia and subsequent recurrence, highlighting the challenge of managing multimodality toxicities during aggressive local control.