KEY POINTS
- A 71-year-old man with cT2N1M0 stage IIB squamous-cell lung carcinoma received four cycles of albumin-bound paclitaxel, carboplatin, and nivolumab. Treatment produced tumor regression but also immune-mediated nephritis and thyroiditis requiring corticosteroids for nearly 3 months.
- Surgery was deferred, and the patient subsequently received carbon-ion radiotherapy to the primary tumor and involved hilar nodes at 48 Gy in 12 fractions over 6.5 weeks. CT at treatment completion showed substantial tumor shrinkage.
- Respiratory symptoms began 3 days after the final fraction. CT subsequently demonstrated extensive bilateral ground-glass opacities and consolidation, including abnormalities outside the irradiated region; bronchoalveolar lavage on day 17 detected 43,427 Pneumocystis jirovecii reads.
- Despite antibiotics and TMP-SMX, respiratory failure progressed to the point of requiring intubation and mechanical ventilation. Methylprednisolone was escalated to 80 mg every 8 hours, doses above 40 mg/day were continued for 35 days, and corticosteroid treatment ultimately lasted 4 months.
- The authors considered checkpoint-inhibitor pneumonitis the predominant process with superimposed Pneumocystis infection rather than conventional radiation pneumonitis. Approximately 6 months after CIRT, bronchoscopic recurrence was documented.
CLINICAL TAKEAWAY
The case illustrates the diagnostic difficulty of severe pulmonary toxicity when thoracic particle therapy follows immunotherapy and prolonged corticosteroid exposure. The timing and imaging led the authors to favor checkpoint-inhibitor pneumonitis, but one heavily confounded case cannot show that carbon-ion RT triggered the event or quantify the risk of this treatment sequence.