Radiologic heterogeneity in responses to anti-PD-1/PD-L1 therapy in metastatic renal cell carcinoma

Radiologic assessment of tumor response remains a challenge in patients treated with immune checkpoint inhibitors. In metastatic melanoma, for example, a spectrum of imaging patterns in response to immunotherapies have been recognized and associated with clinical benefit. In metastatic renal cell carcinoma (mRCC), less than half of patients treated with immune checkpoint inhibitors achieve objective responses, but some of the responses have been durable. In this series, five different imaging patterns of response and progression are described in mRCC patients treated with anti-PD-1/PD-L1 agents: (i) early and complete response, (ii) pseudoprogression, (iii) disease stability before ultimate response, (iv) mixed response with new lesions, and (v) early progression/primary refractory disease. The implications of the different imaging patterns of patient responses on disease prognosis are discussed and highlight the need for individualized patient assessment when using these novel immune-targeted agents.