Sideris, a Modern York patient with advanced colorectal cancer, said she no longer needs chemotherapy or radiation after responding to an experimental immunotherapy in a clinical trial led by Dr. Luis Diaz at Memorial Sloan Kettering Cancer Center.
Immunotherapy eliminated detectable tumors in some patients with metastatic colorectal cancer
In the phase 2 trial, patients with microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) colorectal cancer received dostarlimab, a PD-1 blocking antibody, every three weeks for six months. All 12 participants who completed the regimen showed complete clinical remission, with no evidence of disease on imaging, endoscopy, or biopsy, and none required subsequent chemotherapy, radiation, or surgery.
Researchers caution that long-term data and broader applicability remain uncertain
Dr. Diaz noted that while the results are unprecedented, the trial was small and lacked a control group, making it impossible to determine whether the immunotherapy alone caused the remissions or if other factors played a role. He emphasized that more studies are needed to confirm durability of response and to identify which patients are most likely to benefit, as not all tumors respond to immune checkpoint inhibitors.
For more on this story, see Masked Immunotherapy: New Cancer Drug Shows Promise in Prostate Cancer Trials.
This approach builds on prior successes but faces hurdles in wider adoption
Last time immunotherapy showed similar promise in colorectal cancer was in 2017, when pembrolizumab received FDA approval for MSI-H/dMMR tumors based on earlier phase 2 data, though response rates were lower and not all patients achieved complete remission. Experts warn that manufacturing costs, biomarker testing requirements, and unequal access to specialized centers could limit real-world impact, even if larger trials confirm these findings.
This follows our earlier report, Early-Onset Colon Cancer Deaths Linked to Lower Education Levels.
What type of colorectal cancer patients responded to the immunotherapy in this trial?
Patients with microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) metastatic colorectal cancer were included in the trial, as these tumors are more likely to respond to immune checkpoint blockade due to their high mutation burden.
Did any patients in the trial need further treatment after immunotherapy?
No, none of the 12 patients who completed the six-month dostarlimab regimen required chemotherapy, radiation, or surgery afterward, as all showed complete clinical remission with no detectable disease.