Recent advances in immunotherapy preceded the approval of programmed cell death 1 (PD-1) inhibitors for the treatment of a variety of cancer types, including melanoma, renal cell carcinoma, non-small cell lung cancer (NSCLC), head and neck squamous cell carcinoma (HNSCC), and Hodgkin lymphoma. These agents are, however, associated with numerous immune-mediated adverse reactions.1,2

Among these immune-related toxicities, pneumonitis has been reported as a rare adverse event, though it is potentially life-threatening. Knowledge of the incidence and potential manifestations of immune-mediated pneumonitis may assist clinicians in diagnosing early and treating appropriately this adverse event, which occurs among patients treated with PD-1 blockade.

According to a meta-analysis published in JAMA Oncology, which included 4496 PD-1 inhibitor-treated patients from 20 studies, the overall incidence of pneumonitis during PD-1 inhibitor monotherapy was 2.7% (95% CI, 1.9-3.6) for all-grade and 0.8% (95% CI, 0.4-1.2) for grade 3 or higher pneumonitis.3

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Patients with NSCLC treated with PD-1 inhibitor therapy have odds 43% higher of developing all-grade pneumonitis, and a nearly 3-fold higher risk of developing grade 3 or higher pneumonitis, than patients with melanoma. Patients with RCC also had a 59% higher chance for all-grade pneumonitis than those with melanoma.

Combination therapy was associated with higher odds than monotherapy for all-grade and grade 3 or higher pneumonitis. These findings highlight the importance of clinician awareness of the potential for patients treated with these agents to develop this reaction and other immune-mediated adverse events.