SNAP, CRACKLE, AND POP: A CASE OF PEMETREXED-INDUCED INTERSTITIAL PNEUMONITIS

Abstract

TOPIC: Diffuse Lung Disease TYPE: Medical Student/Resident Case Reports INTRODUCTION: Pemetrexed is a folic acid inhibitor which is used for the treatment of non-small cell lung cancer (NSCLC) (1). Pemetrexed is generally well tolerated, but interstitial pneumonitis is an exceedingly rare, potentially fatal adverse effect (2). The diagnosis of drug induced interstitial pneumonitis is one of exclusion and based on nonspecific clinical and radiographic findings. Onset of symptoms must correlate clinically with timing of administration of the offending agent, and the symptoms improve with removal of the medication and initiation of corticosteroids (3). It is important for clinicians to have a high index of suspicion to initiate early treatment, reducing morbidity and mortality. Below is a case of a patient with lung adenocarcinoma who developed pemetrexed induced interstitial pneumonitis. CASE PRESENTATION: Our patient is an 85 year old man who was diagnosed with stage IVA lung adenocarcinoma. He received two cycles of Carboplatin and Pemetrexed with good radiologic response but experienced intolerable side effects. The decision was made to transition to Pemetrexed monotherapy. Two weeks after his second cycle, he developed dyspnea, low grade fevers and fatigue, requiring supplemental oxygen (Vapotherm 60% FiO2 at 40 L/min) and hospital admission. Physical exam was notable for diffuse crackles bilaterally. CTA Chest demonstrated bilateral ground glass opacities and was negative for pulmonary embolism. He was empirically started on broad spectrum antibiotics for multifocal pneumonia. COVID-19, respiratory viral test, blood and sputum cultures were all negative. Bronchoscopy with bronchoalveolar lavage (BAL) demonstrated normal airways. There was no evidence of alveolar hemorrhage. BAL cell count and differential was notable for a lymphocytic predominance. BAL cytology demonstrated pulmonary macrophages and mixed inflammatory cells but no atypical cells. High dose corticosteroids were started on hospital day five. Oxygen requirement steadily decreased, and he was discharged a few days later on 2 L NC and a prolonged corticosteroid taper. DISCUSSION: Pemetrexed is a widely used first-line treatment for NSCLC. Pemetrexed-induced interstitial pneumonitis has a range of clinical presentations, making it challenging to diagnose. Presentations vary from asymptomatic to life-threatening requiring mechanical ventilation. Moreover, it is a very rare side effect of Pemetrexed. This case highlights the importance of having strong clinical suspicion so that interstitial pneumonitis can be identified and treated early, mitigating morbidity and mortality. A thorough workup must be completed to rule out other causes, especially infection. CONCLUSIONS: Through early diagnosis, pemetrexed can be discontinued and corticosteroids can be initiated sooner, reducing risk to the patient and improving clinical outcomes (3). The patient should not be rechallenged with Pemetrexed, as this could be fatal. REFERENCE #1: Dhakal, B., Singh, V., Shrestha, A., Rao, A., & Choong, N. (2011). Pemetrexed induced pneumonitis. Clinics and Practice 1(4), 232-6. DOI: 10.4081/cp.2011.e106 REFERENCE #2: Kim, KH. et al. (2013). Interstitial pneumonitis after treatment with pemetrexed for non-small cell lung cancer. Cancer Research and Treatment 45(1), 74-7. DOI: 10.4143/crt.2013.45.1.74 REFERENCE #3: Skeoch, S. et al. (2018). Drug-induced interstitial lung disease: A systematic review. Journal of Clinical Medicine 7(10), 1-30. DOI: 10.3390/jcm7100356 DISCLOSURES: No relevant relationships by Brent Bagley, source=Web Response No relevant relationships by Ethan Tope, source=Web Response