Background and objectives: Objective response as determined by Response Evaluation Criteria in Solid Tumors (RECIST) is low among patients with metastatic renal cell carcinoma (mRCC) treated with targeted agents, despite significantly improved progression-free survival (PFS). A modified response threshold may be more clinically meaningful than RECIST for identifying patients who may derive a PFS benefit from targeted therapy.
Patients and methods: We performed a retrospective analysis of data from the phase III RECORD-1 trial of everolimus versus placebo in patients with mRCC who had failed sunitinib or sorafenib (ClinicalTrials.gov identifier: NCT00410124). A series of tumour response thresholds, defined by the best change in the sum of the longest tumour diameters (ΔSLD) of target lesions, was evaluated to distinguish 'responders' from 'non-responders' with respect to significant improvement in PFS.
Results: The optimal threshold for determining a response to everolimus was -5% ΔSLD. At this threshold, median PFS was 8.4 months in responders and 5.0 months in non-responders (hazard ratio [HR] 2.4, 95% confidence interval [CI] 1.6-3.7).
Conclusion: In patients who have failed vascular endothelial growth factor receptor-tyrosine kinase inhibitor (VEGFr-TKI) therapy, everolimus affords superior PFS to placebo, regardless of change in tumour burden. However, a ≥ 5% reduction in SLD is a better predictor of PFS benefit than the classical ≥ 30% reduction used with RECIST.
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