25: Comprehensive Evaluation of Response to Immune Checkpoint Blockade in Primary Tumor: Radiographic and Radiomic Features Predict Pathologic Response in Primary Tumor

Background: Immune checkpoint blockade (ICB) alone and in combination has dramatically improved outcomes in metastatic renal cell carcinoma (RCC), however there is currently a paucity of biomarkers to predict response to ICB.

Methods: We identified 185 patients who received systemic immune checkpoint blockade (IO/IO or IO/TKI) from 2015 to 2022 with a diagnosis of renal cell carcinoma. Of the 185 patients, 62 patients had the primary kidney tumor present. In sub-groups of patients with the primary tumor present, we recorded radiographic information, including time of initial treatment through treatment failure and receipt of second-line therapy or surgical intervention, the radiographic kinetics of response to therapy, RECIST measurements and 145 radiomic features. Pathologic data was reviewed and recorded.

Results: A 1:1 response in change in primary vs. metastatic tumor volume over the study period was noted, however there were outliers who primarily had changes in metastatic sites of disease and vice versa. Maximal tumor shrinkage did not vary between patients receiving IO/IO vs. IO/TKI (p=0.41) and kinetics of radiographic change were not associated with clinical outcomes. Change in size of primary tumor from diagnostic scan to scan prior to surgery (p=0.002) and pre-operative contrast enhancement of the primary tumor (p=0.02) was associated with residual viable tumor on pathology. When examining radiographic features of response to systemic therapy, we noted four 1st and 2nd order radiomic features that identified patients with minimal residual disease on pathologic evaluation.

Conclusions: Herein we provide a comprehensive clinical, radiographic and pathologic evaluation of patients with metastatic renal cell carcinoma with primary tumor intact. This information is important in helping quantify clinical response in patients receiving systemic therapy and may be important in guiding treatment decisions and delineating prognosis.