Clinically meaningful outcomes in refractory metastatic colorectal cancer: a decade of defining and raising the bar.

Currently, there is no consensus definition for clinically meaningful outcomes in randomized clinical trials (RCTs) designed to evaluate new treatments for patients with refractory metastatic colorectal cancer (mCRC). Since 2014, recommended targets for improvements in overall survival and progression-free survival have been published by several societies, including those from the American Society of Clinical Oncology (ASCO) Clinically Meaningful Outcomes Working Group in 2014, the European Society for Medical Oncology-Magnitude of Clinical Benefit Scale (ESMO-MCBS) in 2015, and Colorectal Cancer Canada (CCC) consensus statements in 2019. However, evidence from several systematic reviews suggests that in a substantial proportion of RCTs that led to oncology drug approvals, the recommended thresholds of ASCO and ESMO-MCBS were not met. In addition to efficacy and safety, quality of life (QoL) is important to patients with mCRC, especially for those who are receiving later-line therapy or end-of-life care. As such, both ESMO-MCBS and CCC recommend the inclusion of QoL assessments in the design of mCRC clinical trials. Since the publication of the ASCO recommendations in 2014, there has been significant progress in the development of treatment options for patients with refractory mCRC; these include the approvals of trifluridine/tipiracil (FTD/TPI) as a single agent and in combination with bevacizumab, and the approval of fruquintinib. Among the phase III RCTs in third-line mCRC, only the SUNLIGHT trial of FTD/TPI plus bevacizumab met all recommended thresholds for clinically meaningful improvements, while also demonstrating a manageable safety profile and slower deterioration in multiple measures of QoL compared with FTD/TPI alone. The results from the SUNLIGHT study show that incremental gains in several clinically meaningful endpoints are achievable, thus raising the bar in defining clinically meaningful outcomes for emerging therapies in refractory mCRC.