Key Takeaways from STELLAR 303 and Implications for Treating MSS Metastatic Colorectal Cancer

Dr. Saeed summarizes the principal clinical lessons from STELLAR 303 and their implications for the management of refractory MSS metastatic colorectal cancer. He identifies the trial as the first immunotherapy-based study to demonstrate a positive overall survival outcome in this population, with clean, large-scale data supporting its use as a third-line approach. Benefit was consistent across prespecified subgroups, including patients with liver metastasis, those with RAS-mutated disease, and those with prior bevacizumab exposure, the last of which is particularly relevant given that nearly all patients treated in the United States will have received bevacizumab in earlier lines. Dr. Saeed contrasts this favorably with sunlight data, in which prior bevacizumab exposure attenuated benefit from trifluridine-tipiracil plus bevacizumab. He concludes that zanzalintinib plus atezolizumab represents a viable universal third-line strategy, with particular confidence in patients without liver metastasis pending maturation of the non-liver metastasis overall survival endpoint.