FDA Clears First Immunotherapy to Replace Surgery for a Subset of Rectal Cancer Patients

On October 19, 2026, the FDA granted accelerated approval to dostarlimab (Jemperli, GSK) as a standalone treatment for adults with previously untreated, stage II or III locally advanced rectal cancer that is mismatch repair deficient (dMMR) or microsatellite instability-high (MSI-H) — a molecular subtype found in roughly 3% to 10% of rectal cancers. The decision, based on interim results from the 154-patient AZUR-1 trial, marks the first time the agency has cleared an immunotherapy to potentially let a defined group of rectal cancer patients skip surgery, radiation, and chemotherapy entirely. This article explains what the data actually showed, who qualifies, and the real limitations that come with an accelerated approval based on interim, uncontrolled results.

A Genuinely Different Treatment Path

For decades, locally advanced rectal cancer has meant some combination of chemotherapy, radiation, and surgery — often a permanent colostomy, plus long-term bowel, bladder, and sexual side effects. The idea that a subset of patients might avoid all of that with an IV infusion every three weeks has circulated in oncology since researchers first reported, in a small 2022 study, that every one of their dMMR/MSI-H patients treated with dostarlimab alone showed no detectable tumor afterward. That early signal — 50 patients, zero cancers found post-treatment, 93% still cancer-free at 12 months — was striking enough to earn Breakthrough Therapy designation, but it was far too small to support approval on its own.

AZUR-1 was designed to test that signal at a larger, registrational scale. It enrolled 154 patients who received up to nine infusions of dostarlimab over about six months, with a median follow-up beyond two years — meaningfully longer than many accelerated-approval trials. The FDA's own clearance now rests on this trial, reviewed under Project Orbis and the Commissioner's National Priority Voucher pilot, which moved the decision roughly four months ahead of its original February 2027 target.

What the Data Actually Showed

The headline result is organ preservation: 71% of all 154 treated patients (110 people) received dostarlimab alone with no additional surgery, radiation, or chemotherapy and no disease progression. Another 17% eventually had surgery, and 8% needed additional systemic therapy or radiation — meaning roughly 1 in 4 patients still required some form of the conventional treatment this approval is meant to help patients avoid.

On the trial's primary endpoint — a 12-month clinical complete response (cCR12) — the results depend on who is counting. An independent central review of 116 evaluable patients found a 47% cCR12 rate; the trial's own investigators, assessing 144 evaluable patients, reported 68%. GSK has attributed part of that gap to immaturity in the data, noting that roughly 38 additional patients had achieved a complete response but had not yet reached the 12-month mark at the data cutoff. That is a real and still-unresolved discrepancy, not a rounding difference, and it is one of the clearer signs that this is an interim readout rather than a finished picture.

What It Means for Patients

For the small slice of rectal cancer patients whose tumors carry the dMMR/MSI-H biomarker, this approval is a meaningful and rare kind of good news: a realistic chance, backed by two independent studies now, of avoiding a permanent colostomy and the lasting effects of pelvic radiation and radical surgery. It is also a genuine first — the FDA has not previously approved an immunotherapy-alone pathway as a substitute for standard local therapy in this cancer.

It is not, however, a cure-all, and it is not for most rectal cancer patients. Biomarker testing with an FDA-authorized test is required before anyone can be considered, and the agency's own estimate puts the eligible dMMR/MSI-H population at only about 3% of locally advanced rectal cancer cases (GSK cites a broader 5%–10% range). The remaining 90%-plus of rectal cancer patients are not affected by this approval at all.

Caveats That Matter

This is an accelerated approval, not a full one — a regulatory category reserved for promising but not-yet-fully-confirmed results, which legally requires GSK to continue following patients to verify that these responses translate into durable, lasting clinical benefit. Several specific gaps remain open:

The trial had no control arm. AZUR-1, like the earlier study, was single-arm and open-label, so there is no randomized comparison against standard chemoradiation plus surgery — only a comparison to historical outcomes.

Long-term recurrence risk is still unknown. Even in the smaller, longer-running cohort, 1 of 27 patients followed for three-plus years had a recurrence. With median AZUR-1 follow-up just over two years, how durable these responses are at five or ten years is simply not yet known.

The side-effect profile is not trivial. Jemperli works by releasing a brake on the immune system, which means it can also cause the immune system to attack healthy organs — reactions the FDA label states can be severe or fatal. In AZUR-1, 20% of patients had a serious adverse reaction and 3% permanently stopped treatment because of side effects; the most common reactions were fatigue (32%), rash (22%), diarrhea (18%), and itching (17%).

Access and cost are unresolved. As with most newly approved biologics, insurance coverage, prior authorization requirements, and out-of-pocket cost are not yet settled and will likely vary by payer.

What's Next

GSK is expected to present fuller interim AZUR-1 data at a major oncology congress in the coming months, which should help clarify the gap between the independent and investigator-assessed response rates. Longer follow-up from the same trial will also be needed to determine how many of these clinical complete responses hold up over three, five, and ten years — the real test of whether "no detectable cancer" today means a durable cure. Patients considering this option should discuss eligibility testing and the trade-offs of forgoing standard local therapy directly with their oncology team, since the decision to try to avoid surgery carries its own risks if the disease is not fully controlled.

Bottom Line

The October 19, 2026 FDA accelerated approval of dostarlimab for dMMR/MSI-H locally advanced rectal cancer is a real and encouraging advance — the first time immunotherapy alone has been cleared as a potential substitute for surgery, radiation, and chemotherapy in this disease, letting roughly 7 in 10 trial patients avoid those treatments altogether. It is just as important to hold onto what it is not: a cure confirmed by long-term data, an option for the large majority of rectal cancer patients who lack this specific biomarker, or a treatment free of serious immune-related risk. This is promising, well-documented progress for a narrow biomarker-defined population — not yet a settled, universal answer for rectal cancer.