Abstract Introduction Patients with malignancy often receive chemoradiation. The presentation, management, and prognosis of checkpoint inhibitor/immunotherapy-induced (CTxI) or radiotherapy-induced (RTI) pneumonitis differ slightly. Delineating them from each other and when they are present together is challenging. Case Description 60-year-old male with past medical history of metastatic esophageal squamous cell cancer s/p treatment with chemotherapy Nivolumab and Iplimumab started 2/2025, and discontinued 6/2025 2/2 disease progression. Patient underwent palliative radiation of the right thorax on 7/2025. Patient presented to us on 8/2025 with shortness of breath and respiratory distress. The infectious workup with bronchial washings was negative, and the patient had neither a white blood cell count nor fever. Negative workup for pulmonary embolism, and rest h/o unremarkable. The imaging results revealed pulmonary congestion in the left lung (Fig. 1). The findings for new metastatic spread were unremarkable.Furthermore, a biopsy of the lung tissue was denied per the patient’s request. The plan was to manage as a checkpoint inhibitor pneumonitis as a severe grade III. He was subsequently treated with high-dose prednisone long taper. Patient responded well to initial therapy and improved imaging 4 weeks after(Fig 2), but could not tolerate doses less than 0.5mg/kg/d as was rehospitalized with the same episode, which responded quickly to high-dose prednisone. Of note, no history of lung pathology in the past. Discussion Generally, CTxI pneumonitis occurs symmetrically or diffusely, as opposed to RTI pneumonitis. Although it is not uncommon to have pneumonitis outside the radiotherapy zone, the so-called migratory organizing pneumonitis is prevalent in about 2/3rd of cases where findings away from the irradiated zone do occur. Generally, CTxI pneumonitis has a slightly higher tendency to recur than radiation pneumonitis. Our case would represent an overlapping case of RTI pneumonitis with a component of CTxI. The lungs seemed to be primed by the chemotherapy, on which radiation led to synergistic damage to the contralateral healthy lung. Further, the discordance between computed tomography (CT) images and chest xray indicate evolving nature (possible fibrosis) of lung injury which are being detected by CT only. Conclusion The radiation pneumonitis in patients also on CTxI is important to consider during the decision of palliative radiation, as it can increase morbidity on the background of CTxI pneumonitis. While pointing out one etiology may be challenging, timeline, and pattern of presentation can guide the judgement. This abstract is funded by: None
Sharma et al. (Fri,) studied this question.