Local Therapy for Isolated Residual Metastatic Melanoma and Renal Cell Carcinoma Following Immune Checkpoint Inhibition Leading to Long-Term Remission.

Immune checkpoint inhibitors (ICI) have revolutionized the treatment of melanoma and renal cell carcinoma (RCC). Immune therapy response outcomes are based on radiographic measurements of cancer sites alone, without considering whether these sites contain a viable tumor that has metastatic potential. We hypothesized that ICI may lead to residual radiographic abnormalities that either contain nonviable tumor or tumor without metastatic potential that could be controlled with local therapy. In this retrospective cohort study, we identified 8 patients with melanoma and 4 with RCC who had an operable residual metastasis after major tumor response to ICI treatment. On the basis of histologic analysis, 10 (83.3%) of the resected samples showed viable tumor while 2 (16.7%) showed no viable tumor cells on pathology. After surgical removal (11), or radiosurgery (1), to the lesion, all patients had no evidence of melanoma or RCC recurrence for the duration of follow-up. Time from definitive treatment to last follow-up was a mean of 5.9 years (1.1-11.9 y). ICI therapy in melanoma and RCC may lead to a response where existing lesions or new lesions either have no viable cancer or lose their metastatic capacity. Surgical removal or local radiation to those lesions with residual cancer can render patients' long-term disease-free without the need for additional systemic therapy. Consideration of local therapy approaches in patients with isolated residual metastatic disease after ICI response is clinically justified.