Stefan Moore, Chairman and CEO of Cancer Response Team, shared a post on X:
“A major breakthrough in cancer treatment highlights the extraordinary potential of immunotherapy for a specific subtype of Rectal Cancer
In a phase 2 clinical trial led by Memorial Sloan Kettering Cancer Center, the drug dostarlimab (Jemperli) achieved a 100% clinical complete response rate in patients with locally advanced mismatch repair deficient (dMMR) rectal cancer. All patients who completed treatment showed no detectable signs of cancer on imaging scans, endoscopy, biopsies, or clinical exams, allowing them to avoid surgery, radiation, and chemotherapy.
Dostarlimab is a PD-1 checkpoint inhibitor that blocks a pathway cancer cells use to evade the immune system. This enables the body’s own immune defenses to precisely recognize and destroy cancer cells, without the broad tissue damage caused by traditional treatments.
Patients in the trial received dostarlimab intravenously every three weeks for six months, followed by close monitoring. As of the latest updates in 2025, the 100% complete response rate has held in cohorts of up to 49 patients with dMMR rectal cancer, with many sustaining responses beyond two years.
This approach spared patients severe side effects of standard rectal cancer treatments, such as permanent bowel, urinary, or sexual dysfunction, infertility, or the need for a colostomy.
This remarkable outcome applies only to dMMR rectal cancer, a genetic subtype that accounts for about 5-10% of cases and is particularly sensitive to immunotherapy. It does not apply to the majority of rectal cancers.
The trial cohorts remain relatively small and longer term follow up is ongoing. Larger, multicenter confirmatory trials (such as AZUR-1) are in progress and the FDA has granted Breakthrough Therapy Designation to accelerate development. If validated in broader studies, this could transform care for this subtype by prioritizing targeted immunotherapy over invasive treatments.”
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