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Background: PD-1 inhibitor-related pneumonitis is an uncommon but serious immune-related adverse event irAE . Details of radiographic patterns of this entity remain to be investigated. Methods: Patients pts ho developed PD-1 inhibitor-related pneumonitis ere identified among those treated in trials of nivolumab for advanced melanoma, lung cancer, and lymphoma. Chest CTs ere revieed by a consensus of 3 radiologists to assess CT findings and radiographic patterns of pneumonitis according to ATSERS classification of interstitial pneumonias, hich ere compared across tumor types and treatment regimens. Results: Among 170 pts treated in 10 different trials of nivolumab, either alone or in combination, 20 pts developed pneumonitis as an irAE Grade: 1 in 5; 2 in 10; 3 in 5 pts . Of these, 13 65 percent ere female, median age as 52 range 28-71 ; 5 received nivolumab alone and 15 received combination therapy ith ipilimumab in 12, lirilumab in 3 . Ten pts had melanoma, 6 had lymphoma, and 4 had lung cancer. Median time from therapy initiation to pneumonitis as 2.6 months range 0.5-11.5 , and as shorter in lung cancer than others 1.1 vs. 3.1 months; p = 0.008 . Most pts 1720; 85 percent received corticosteroids; 3 15 percent also required infliximab. Among 19 pts ith available CT, ground glass opacities ere noted in all pts, ith consolidation in 11. The most common distribution as multifocal n = 9 , folloed by peripheral and loer n = 3 and diffuse n = 3 . Radiographic pattern as cryptogenic organizing pneumonia COP in 12, non-specific interstitial pneumonia NSIP in 3, hypersensitivity pneumonitis HP in 2, and acute interstitial pneumonia AIP acute respiratory distress syndrome ARDS in 2 pts. AIPARDS pattern had the highest pneumonitis grade, folloed by COP, hile NSIP and HP had loer grade median Grade: 3,2,1,1, respectively; p = 0.005 . COP as the most common pattern in all tumors and treatment regimens. Conclusions: PD-1 pneumonitis shoed a spectrum of radiographic patterns, hich ere associated ith toxicity grades of pneumonitis. COP as the most common pattern across tumor types and therapeutic regimens. The radiographic pattern-based approach may contribute to better diagnose, categorize, and prognosticate in this entity.,J Clin Oncol 34, 2016 suppl; abstr 3053 00:00.0,Developmental TherapeuticsImmunotherapy