Chronic Pleuritis and Recurrent Pleural Effusion After Atezolizumab for Small Cell Lung Cancer

BACKGROUND As use of immune checkpoint inhibitors consistently grows, so does knowledge of immune-related adverse events. Pleural complications from PD-L1 inhibitors such as atezolizumab have never been reported. We describe the first reported case of biopsy-proven pleuritis manifesting as recurrent pleural effusion in a patient treated with atezolizumab. CASE REPORT A 66-year-old woman with history of extensive-stage small cell lung cancer presented with a new pleural effusion. She was previously treated with carboplatin, etoposide, and atezolizumab followed by atezolizumab maintenance, but this later was stopped due to pneumonitis. She had been on no systemic therapy for 6 months prior; radiation to the chest was completed 1 year earlier. Thoracentesis revealed an exudate with eosinophilia but no malignancy. She underwent medical thoracoscopy, which showed normal pleura with no evidence of radiation changes. Random pleural biopsies revealed only chronic pleuritis. Given normal-appearing pleura, radiation pleuritis was ruled out. It was felt that the chemotherapy had occurred too long ago to be a present cause of her pleuritis. As such, after extensive workup, the eosinophilic pleural effusion was felt to be due to pleuritis from atezolizumab. The effusion has ultimately recurred 5 times over 1 year, and cytology remains negative for malignancy. CONCLUSIONS Patients with prior cancer presenting with a new pleural effusion should undergo an extensive workup to evaluate for recurrence. When other causes have been ruled out, ongoing immune-related effects of immunotherapy should be considered. Pleural complications from PD-L1 inhibitors have not been reported; we present a possible case of chronic pleuritis and recurrent effusion due to atezolizumab.