A Rectal Cancer Immunotherapy That Lets Some Patients Skip Chemo, Radiation, and Surgery

For decades, locally advanced rectal cancer meant the same brutal sequence: chemotherapy, radiation, then surgery that often left patients with a permanent colostomy bag. On October 19, 2026, the FDA granted accelerated approval to dostarlimab (Jemperli) for MSI-H or dMMR locally advanced rectal cancer. For some patients, that sequence may now be skipped entirely.

Key Takeaways

• On October 19, 2026, the FDA granted accelerated approval to dostarlimab (Jemperli) for adults with Stage II/III locally advanced rectal cancer that is MSI-H or dMMR (FDA, 2026).
• The drug may allow some patients to avoid chemotherapy, radiation, and surgery, which can have lasting effects on daily life (FDA, 2026).
• Eligibility requires an FDA-authorized test confirming MSI-H or dMMR status (FDA, 2026).
• Dostarlimab previously held breakthrough therapy designation for this use (FDA, 2026).

What Did the FDA Approve?

Dostarlimab is an immunotherapy that blocks PD-1, releasing the immune system to attack tumor cells. The new approval covers adults with Stage II or III locally advanced rectal cancer whose tumors are microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR), confirmed by an FDA-authorized test (FDA, 2026). The approval was granted under priority review with breakthrough therapy designation (FDA, 2026).

Citation capsule: Dostarlimab (Jemperli) received FDA accelerated approval on October 19, 2026 for MSI-H/dMMR locally advanced rectal cancer, potentially sparing some patients chemotherapy, radiation, and surgery (FDA, 2026).

Who Qualifies for This Approach?

Only patients whose tumors test MSI-H or dMMR on an FDA-authorized assay qualify (FDA, 2026). That subset is roughly 5 to 10 percent of rectal cancers. Patients with proficient mismatch repair tumors follow the standard chemoradiation-and-surgery pathway. Testing should happen early, before treatment starts, because it changes the plan (FDA, 2026).

Citation capsule: Eligibility requires MSI-H or dMMR status on an FDA-authorized test, covering roughly 5-10% of rectal cancers; others follow standard care (FDA, 2026).

Why Does Avoiding Surgery Matter So Much?

Rectal surgery and pelvic radiation can damage bowel, bladder, and sexual function for life. A colostomy bag changes how patients eat, dress, and socialize. An immunotherapy that controls the tumor without those steps is not just more convenient; it preserves quality of life (FDA, 2026).

Citation capsule: Avoiding rectal surgery and pelvic radiation preserves bowel, bladder, and sexual function and prevents permanent colostomy for eligible patients (FDA, 2026).

What Are the Trade-Offs and Risks?

Immunotherapy carries its own risks: colitis, pneumonitis, hepatitis, and thyroid dysfunction are possible. Not every MSI-H tumor responds, and some patients still need surgery later. Accelerated approval means confirmatory trials must verify long-term benefit (FDA, 2026).

Citation capsule: Dostarlimab can cause immune-related colitis, pneumonitis, hepatitis, and thyroid dysfunction; non-responders may still need surgery, and confirmatory trials are required (FDA, 2026).

How Should Patients and Families Use This News?

Ask for MSI/MMR testing before starting treatment. If positive, discuss dostarlimab with an oncologist at a center experienced in immunotherapy. If negative, the standard pathway remains effective and well studied (FDA, 2026).

Citation capsule: Patients should request MSI/MMR testing before treatment and discuss dostarlimab with an experienced oncologist if positive (FDA, 2026).

Frequently Asked Questions

Does dostarlimab replace surgery for all rectal cancer patients?

No. Only MSI-H or dMMR tumors qualify; most patients still need standard care (FDA, 2026).

Is this approval final?

It is accelerated approval, contingent on confirmatory trials showing lasting benefit (FDA, 2026).

How is MSI-H or dMMR status determined?

By an FDA-authorized test on tumor tissue (FDA, 2026).

What side effects should patients watch for?

Immune-related colitis, pneumonitis, hepatitis, and thyroid problems (FDA, 2026).

Conclusion

For the small but important group of MSI-H rectal cancer patients, dostarlimab offers a chance to beat the disease without losing bowel or bladder function. Testing and specialist discussion are the next steps.

Sources

• U.S. FDA. FDA approves immunotherapy that may allow certain patients with rectal cancer to avoid chemotherapy, radiation, and surgery. October 19, 2026. Retrieved 2026-10-26. https://www.fda.gov/news-events/press-announcements/fda-approves-immunotherapy-may-allow-certain-patients-rectal-cancer-avoid-chemotherapy-radiation-and