Monitoring the response to immunotherapy in PD-L1-positive lung adenocarcinoma using 18F-FDG PET/CT

A 74-year-old patient was being monitored by Internal Medicine for generalized bone pain and arthralgia, a history of treated prostate cancer, and multiple cardiovascular risk factors. Given the suspicion of inflammatory or metastatic bone disease, an 18F-FDG PET/CT scan was requested, which showed hypermetabolic cervical-mediastinal lymphadenopathy and an ametabolic pulmonary micronodule. An echobronchoscopy was performed, obtaining a positive biopsy of the subcarinal lymph node, consistent with stage IV lung adenocarcinoma, with 95% PD-L1 expression. Treatment with pembrolizumab was initiated, with complete metabolic response observed from the first follow-up. The patient’s progress was favorable until treatment was suspended due to immune-mediated nephritis. In check-ups, the patient remains in complete metabolic remission. The basis of immunotherapy, its role in the treatment of non-small cell lung cancer, and the usefulness of PET/CT in diagnosis and follow-up are analyzed.