Tumor responses to immunotherapy are highly variable in onset and duration. Responses are often delayed and follow what appears to be progression. However, rapid responses also happen and can result in the disappearance of large lesions, leaving holes and cavities in their wake. To the Editor: Both ipilimumab 1 (anti–cytotoxic T-lymphocyte–associated antigen 4 monoclonal antibody) and nivolumab 2 (anti–programmed death 1 monoclonal antibody) have been approved by the Food and Drug Administration for the treatment of metastatic melanoma on the basis of increased progression-free and overall survival. A phase 1 trial of a combination of ipilimumab and nivolumab showed that 53% of patients had at least 80% tumor shrinkage. 3 We currently have treated 13 patients with melanoma with this combination as part of an expanded-access program (ClinicalTrials.gov number, NCT02186249), and we have observed a remarkable tumor response in 1 patient. The patient is a 49-year-old . . .