Treatment of Pneumonitis

Severity-Based Treatment Algorithm

The American College of Physicians recommends that for drug-induced pneumonitis, treatment is severity-based: grade 1 requires monitoring only, grade 2 requires drug discontinuation plus oral prednisone 1 mg/kg daily, and grade 3-4 requires hospitalization with high-dose IV methylprednisolone 2-4 mg/kg/day 1, 2
For grade 1 pneumonitis, continue the causative therapy with close monitoring, and corticosteroids are not required at this stage, with monitoring of symptoms and oxygen saturation every 2-3 days using pulse oximetry 1, 2
For grade 2 pneumonitis, immediately discontinue the suspected causative agent and initiate oral corticosteroids: prednisone 1 mg/kg daily or equivalent, with tapering over 4-6 weeks minimum after clinical recovery 1, 2
For grade 3-4 pneumonitis, hospitalize immediately and permanently discontinue the offending agent, and administer high-dose IV corticosteroids: methylprednisolone 2-4 mg/kg/day or equivalent 1, 2

Improvement following drug cessation without glucocorticoid therapy strongly supports drug-related pneumonitis, with clinical improvement with glucocorticoid therapy supporting but not definitively confirming the diagnosis 1, 2

The American Society of Clinical Oncology notes that anti-PD-1/PD-L1 monoclonal antibodies cause pneumonitis in 2-4% of patients, with grade 3-4 events in 1-2% and fatal pneumonitis in 0.2% 2
Combination immunotherapy increases pneumonitis risk 3-fold, with incidence reaching 10% versus 3% for monotherapy, according to the National Comprehensive Cancer Network 2

The American Thoracic Society recommends reassessing clinical response on Days 2 and 3: checking temperature, white blood cell count, chest X-ray, oxygenation, purulent sputum, hemodynamic changes, and organ function 3