Elective Checkpoint Inhibitor Discontinuation in Metastatic Solid Tumor Patients: A Case Series.

Introduction: Checkpoint inhibitor (CKI) therapy has markedly altered the survival of patients with many solid tumors. It appears clear that 10-40% of patients with a number of metastatic cancers can achieve lengthy remissions following CKI therapy. The optimal duration of treatment or whether treatment can ever be safely stopped is still controversial. Based on melanoma-derived data, we tested whether CKI treatment could safely be discontinued in patients with other solid tumors. Methods: A retrospective analysis was performed in adults with metastatic solid tumors treated with CKI-based therapy. Patients with solid tumors who achieved complete remission on 2 sequential scans at least 3 months apart during ongoing treatment were identified from our computerized patient database. Patient data was analyzed for patient characteristics, as well as progression-free and overall survival. Results: A total of 69 non-melanoma solid tumor patients were treated with CKI-based regimens in our clinic and 14 achieved complete remission (20.3%). Five patients were female (35.7%) and the remaining nine were male (64.3%). A 100% progression-free survival was observed for these patients. The median duration of complete remission was over 20 months from the time of elective treatment discontinuation. Median overall survival was not reached in this cohort. One patient died of no cancer-related causes. Conclusions: Based on this retrospective case series, elective treatment discontinuation in patients who achieved complete remission appears feasible. All patients remained in a durable complete remission after treatment discontinuation. We hypothesize that appropriate selection of patients for early treatment discontinuation may decrease their economic burden related to ongoing treatment, limit potential toxicity, and improve quality of life.