Jemperli for Rectal Cancer: Who Could Avoid Surgery?

Who qualifies for Jemperli treatment for rectal cancer?

The October 19 approval requires an FDA-authorized test confirming mismatch repair deficiency, known as dMMR, or high microsatellite instability, called MSI-H. Jemperli, the brand name for dostarlimab-gxly, is used alone. These biomarkers identify a specific subgroup; the approval does not apply to every rectal tumor. [FDA announcement](https://www.fda.gov/news-events/press-announcements/fda-approves-immunotherapy-may-allow-certain-patients-rectal-cancer-avoid-chemotherapy-radiation-and)

Dostarlimab is an antibody that blocks PD-1, a protein on immune-system T cells. Blocking this checkpoint can restore an immune attack against cancer. Tumor testing therefore helps determine whether this treatment approach is appropriate. The National Cancer Institute describes testing for missing mismatch repair proteins and molecular testing for microsatellite instability as ways to identify these abnormalities. [NCI drug explanation](https://www.cancer.gov/about-cancer/treatment/drugs/dostarlimab-gxly), [NCI biomarker overview](https://www.cancer.gov/about-cancer/treatment/types/agnostic-cancer-therapies-hp-pdq)

What did clinical trials show about avoiding surgery?

The FDA based its decision on interim findings from AZUR-1, a phase 2 study involving 154 patients. Treatment comprised up to nine doses over six months. Median follow-up exceeded two years. Accelerated approval requires continued follow-up to confirm lasting clinical benefit; the findings do not establish that every responding patient is cured. [FDA trial assessment](https://www.fda.gov/news-events/press-announcements/fda-approves-immunotherapy-may-allow-certain-patients-rectal-cancer-avoid-chemotherapy-radiation-and)

Separate earlier research provides useful context. In a 2025 New England Journal of Medicine report by Andrea Cercek and colleagues, all 49 rectal cancer patients who completed dostarlimab treatment achieved a clinical complete response and chose nonoperative management. That means examinations and imaging found no remaining detectable cancer. This was a selected group within a phase 2 study, rather than proof of a universal cure or a randomized comparison with surgery. The reported 49-of-49 result should not be confused with the newer AZUR-1 findings, which come from a different study. [Published clinical trial](https://www.nejm.org/doi/full/10.1056/NEJMoa2404512)

What monitoring and side effects should patients expect?

Nonoperative management involves ongoing assessment rather than discharge from cancer care. Rectal examinations, endoscopy and MRI help clinicians assess response and detect possible regrowth. The National Cancer Institute describes intensive follow-up as central to watch-and-wait care. Persistent or returning cancer can require additional treatment, including surgery, so patients need an agreed surveillance plan and access to a multidisciplinary team. [NCI rectal cancer treatment guidance](https://www.cancer.gov/types/colorectal/hp/rectal-treatment-pdq)

Immune checkpoint inhibitors can also activate immune attacks against healthy tissue. Fatigue, rash and diarrhea are recognized side effects; less common complications include inflammation of the lungs, bowel, liver and hormone-producing glands. Patients should receive instructions about which symptoms require prompt contact with their treatment team. Avoiding an operation can be a meaningful benefit, but immunotherapy still requires careful medical supervision. [NCI immune checkpoint inhibitor safety information](https://www.cancer.gov/about-cancer/treatment/types/immunotherapy/checkpoint-inhibitors)