Comparison of Solid Tumor Treatment Response Observed in Clinical Practice With Response Reported in Clinical Trials.

Importance: In clinical trials supporting the regulatory approval of oncology drugs, solid tumor response is assessed using Response Evaluation Criteria in Solid Tumors (RECIST). Calculation of RECIST-based responses requires sequential, timed imaging data, which presents challenges to the method's application in real-world evidence research. Objective: To evaluate the feasibility and validity of a novel real-world RECIST method in assessing tumor burden associated with therapy for a large heterogeneous patient population undergoing treatment in routine clinical practice. Design, Setting, and Participants: This cohort study used physician-abstracted data pooled from retrospective, multisite electronic health record (EHR) review studies of patients treated with anticancer drugs at US oncology practices from 2014 through 2017. Included patients were receiving first-line treatment for thyroid cancer, breast cancer, or metastatic melanoma. Data were analyzed from March through August 2020. Exposures: Undergoing treatment with immunotherapy or targeted therapy. Main Outcomes and Measures: Tumor response was classified according to RECIST guidelines (ie, change in sum diameter of target lesions) post hoc with measurements derived from imaging scans and reports. Results: Among 1308 completed electronic case report forms, 956 forms (73.1%) had adequate data to classify real-world RECIST response. The greatest difference between physician-recorded responses and real-world RECIST-based responses was found in the proportion of complete responses: 118 responses (12.3%) vs 46 responses (4.8%) (P < .001). Among 609 patients in the metastatic melanoma population, complete responses were reported in 112 physician-recorded responses (18.4%) vs 44 real-world RECIST-based responses (7.2%) (P < .001), compared with 11 of 247 responses (4.5%) to 31 of 192 responses (16.1%) across pivotal trials of the same melanoma therapies. Conclusions and Relevance: These findings suggest that comparing tumor lesion sizes and categorizing treatment response according to RECIST guidelines may be feasible using real-world data. This study found that physician-recorded assessments were associated with overestimation of treatment response, with the largest overestimation among complete responses. Real-world RECIST-based assessments were associated with better approximations of tumor response reported in clinical trials compared with those reported in EHRs.