Immunotherapy instead of surgery for mismatch-repair-deficient rectal cancer
Dostarlimab made the tumor disappear for at least a year in about half to two-thirds of patients.
What studies found
In AZUR-1, a single-arm study of 154 people with stage II–III MSI-H or dMMR rectal cancer, up to nine doses of dostarlimab led to a complete clinical response lasting at least 12 months in 47% of evaluable patients by independent central review, or 68% as judged by the study doctors. Those patients were monitored instead of having surgery. An earlier, smaller study reported higher rates: all 49 patients who completed treatment had a complete clinical response. The FDA granted accelerated approval on October 19, 2026.
The catch
No randomized trial yet: this is an accelerated approval based on early results, with a median follow-up of about two years. People on monitoring need checks every 4 months for the first 2 years, then every 6 months. Immune-related side effects can be serious.
What to do
If you have rectal cancer, ask whether your tumor was tested for MMR or MSI status before treatment starts, and whether this approach fits you.
Sources
Rung 3 of 5, Moderate: Consistent observational studies or small trials, not yet confirmed by large trials. How we score
Step by step
For the whole picture, from prevention and screening to treatment and life after, see the colorectal cancer page.
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