Long-term survivor with stage IV lung adenocarcinoma, high PD-L1 expresser

We describe the case of a 59-year-old female former smoker diagnosed in February 2017 with stage IV left upper lobe lung adenocarcinoma, following symptoms of dry cough and dyspnea. Imaging and histopathological studies, including chest radiograph, whole-body CT scan, bronchoscopy, and biopsy of a renal lesion, confirmed metastatic spread to lymph nodes, adrenal gland, and kidney. Molecular profiling showed high PD-L1 expression (90%) and was negative for EGFR mutations, ALK rearrangements, and ROS1 fusions. In June 2017, the patient began first-line immunotherapy with pembrolizumab (200 mg every three weeks), based on KEYNOTE-024 trial criteria. A partial clinical and radiological response was achieved and maintained over two years of treatment. The only immune-related adverse event reported was hypothyroidism. Pembrolizumab was discontinued in June 2019 after 24 months of therapy. In May 2020, disease progression was observed with pulmonary and mediastinal lymph node involvement. Pembrolizumab was reinitiated along with palliative local radiotherapy. Following this second course, treatment was again discontinued, and the patient has maintained a sustained partial response for more than three years to date. This case highlights the potential durability of response to pembrolizumab and supports the ­feasibility of rechallenge in selected patients with advanced NSCLC and high PD-L1 expression.