Abstract Introduction Pralsetinib is a selective RET-inhibitor that can be utilized in NSCLC who are found to have RET-positive driver mutations, 1-2% of all NSCLC. Pralsetinib can cause severe adverse reactions including commonly musculoskeletal pain, constipation, fatigue and serious adverse reactions including neutropenia and less reported pneumonitis. Herein, we present a case of pralsetinib-induced grade 2 pneumonitis. Case Description 65-year-old female presented to the hospital with right-sided facial droop and new-onset slurred speech who underwent acute stroke work-up and found to have solid hyperdense mass in the temporal bone with intracranial extension. On CT Chest, patient was found to have 2.4 x 3.0 cm cavitary mass in right lung with posterior pleural thickening. Subsequent IR core biopsy demonstrated adenocarcinoma of pulmonary origin and further genetic testing revealed RET positivity. Patient was started on Pralsetinib and subsequently developed dyspnea on exertion after her second dose. CTA Chest was notable for bilateral patchy bandlike and ground-glass opacities with architectural distortion representative of pneumonitis likely grade 2 immune-checkpoint inhibitor pneumonitis. Patient was started on Prednisone 40 mg for 14 days followed by a 14-day Prednisone taper. CT chest without contrast upon completion of the steroid taper revealed complete resolution of the ground-glass opacities. In conversation with Oncology team, patient was resumed on Pralsetinib at 50% dose reduction without further symptoms. Discussion Immune checkpoint inhibitors have quickly become standard of care for many different cancer types including lung cancer, melanoma, renal cell carcinoma, and in types of colorectal cancer. While these drugs have been shown to improve overall survival, these medications have also demonstrated several adverse reactions for patients that are specific to type of therapy. For Pralsetinib, the common adverse reactions include musculoskeletal pain (40%), constipation (40%), hypertension (40%), diarrhea (35%), fatigue (38%), and fever (22%). Pneumonitis is a rare complication occurring in 14% of all patients, however, 3.3% of those have symptoms classified as more than grade 2 pneumonitis requiring steroids and in rare critical cases requiring cessation of immunotherapy. As in our case, patient’s upon resolution of either imaging findings or symptoms can be trialed again on immunotherapy at a dose reduction. Herein we present a case of Pralsetinib induced pneumonitis requiring steroid taper and continuation of therapy course at a dose reduction which is a reported rare adverse side effect. This case highlights the need for better understanding of adverse reactions associated with immunotherapy and the impact on disease progression. This abstract is funded by: None
McCauley et al. (Fri,) studied this question.