Cetuximab-Induced Pneumonitis: An Overlooked Complication.

Epidermal growth factor receptor (EGFR) inhibitors have largely been used for head and neck cancers, non-small cell lung cancers, and colorectal cancers (CRC). Reports of interstitial pneumonitis with EGFR inhibitors like gefitinib and erlotinib are present in the literature, but pulmonary toxicity with cetuximab has rarely been reported. We present a case of a 78-year-old male with metastatic CRC involving the brain and lungs who presented with severe pneumonitis, a month after treatment with cetuximab. The patient was started on a chemotherapy regimen of 5-fluorouracil, leucovorin calcium, and irinotecan, and later began immunotherapy with cetuximab. Upon admission, the patient complained of shortness of breath. The CTA showed multifocal bilateral ground-glass opacities. Tests for influenza A and B RT-PCR were negative. Tests for Legionella antigen, strongyloides IgG antibody, histoplasma antibody/antigen, cryptococcal antigen, and HIV were also negative. The serum Fungitell assay was within normal limits. The QuantiFERON Gold Plus test was indeterminate, and the COVID-19 PCR was negative twice. The sputum culture was normal. Bronchoscopy could not be performed due to increased oxygen requirements. After excluding other differential diagnoses, cetuximab-induced pneumonitis was considered. The patient was given high-dose corticosteroid therapy; however, he continued to deteriorate clinically and expired after two weeks of hospital admission. This case emphasizes the need for physician alertness in diagnosing drug-induced lung injury and suggests that other alternative disorders should not be ignored.