What this means for you?
On October 19, 2026, the FDA approved dostarlimab (Jemperli), an immunotherapy, for adults with stage II or III rectal cancer that is dMMR or MSI-H. The benefit is big: for eligible patients, this treatment can replace chemotherapy, radiation, and surgery entirely. Instead of going through all three, you may be able to treat your cancer with immunotherapy alone, and avoid their lasting effects on bowel, bladder, sexual function, and fertility. In the AZUR-1 trial, 71% of patients were treated with dostarlimab alone and needed no further treatment, no chemo, no radiation, and no surgery. It is not for everyone, because only tumors that test dMMR/MSI-H respond this way. Below is who qualifies, what to expect, the possible side effects, and the questions to bring to your care team.
Who qualifies for dostarlimab?
You may be a candidate for dostarlimab if all of the following are true:
- You are an adult with rectal cancer.
- Your cancer is stage II or III (locally advanced, meaning it has grown into nearby tissue or lymph nodes but has not spread to distant organs).
- Your tumor is dMMR or MSI-H, confirmed by an FDA-authorized biomarker test.
- You have not yet started treatment for this cancer.
About 5–10% of rectal cancers are dMMR/MSI-H. The only way to know if yours is one of them is a biomarker test on your tumor tissue, and it can’t be seen on a scan or guessed from your symptoms or stage.
Who doesn’t qualify?
This treatment isn’t the right fit for everyone. It is not approved for people whose situation includes:
- A tumor that is proficient mismatch repair (pMMR) or microsatellite stable (MSS), which is the large majority of rectal cancers, and these tumors don’t respond to immunotherapy the same way.
- Rectal cancer that is stage I, or stage IV (metastatic, spread to distant organs), since the approval covers stage II/III.
- Cancer for which you’ve already begun chemotherapy, radiation, or surgery.
- An unknown biomarker status, so you’d need testing first to find out whether you qualify.
If you don’t qualify for dostarlimab, it does not mean you’re out of options. Standard treatments, including surgery, radiation, and chemotherapy, remain effective, and your care team can walk you through what’s best for your situation.
What are the benefits, and how is it given?
- How it’s given: By IV every three weeks, for nine treatments over about six months. No chemotherapy or radiation.
- The results: In the trial, 71% of patients were treated with dostarlimab alone and needed no other treatment. The formal 12-month complete-response rate was 47% by independent review (68% by the treating doctors’ own assessment). So far, among patients who had a complete or near-complete response, none have seen their cancer come back, after about two years of follow-up (median 26 months).
- If it works: You’ll have regular check-ups (exams, scans, and scopes) instead of surgery.
- If it doesn’t fully work: Surgery, radiation, and chemotherapy are still options.
What are the side effects?
Dostarlimab is generally better tolerated than chemotherapy, but it can still cause side effects. In the AZUR-1 trial, the most common were:
- Fatigue (about 32% of patients)
- Rash (about 22%)
- Diarrhea (about 18%)
- Itchy skin (about 17%)
About 1 in 5 patients (20%) had a serious side effect, and 3% stopped treatment because of one.
Because dostarlimab works by activating your immune system, it can sometimes cause the immune system to attack healthy organs, which are called immune-related side effects. These can affect the skin, bowel, lungs, liver, hormone glands, and other areas, and can appear suddenly, during or even after treatment. They are most manageable when caught early, so tell your care team right away about new diarrhea, rash, trouble breathing, or unusual tiredness. Your team will check your blood and other tests during treatment to watch for these.
How Do I Know If My Tumor Is dMMR/MSI-H?
The only way to know is a biomarker test on your tumor tissue.
- To qualify for this treatment, your dMMR/MSI-H status needs to be confirmed with an FDA-authorized test.
- It can’t be seen on a scan or guessed from your symptoms or stage.
- Because this treatment replaces chemotherapy, radiation, and surgery, testing needs to happen before treatment begins.
- The same test can also reveal inherited risk, like Lynch syndrome, that may matter for your family.
Not sure if you’ve had biomarker testing? We encourage all patients to ask their care team: “Has my tumor had biomarker testing, and what were the results?”
Need help understanding your biomarker report? ChatCRC’s free biomarker report reader can explain your results and help you prepare questions. Start at chatbot.fightcolorectalcancer.org or text 318-242-8272 (318-CHATCRC). Explore more in our Resource Library.
Why Is This Approval Important?
This is the first and only immunotherapy approved for locally advanced rectal cancer. For many patients, it may mean avoiding chemotherapy, radiation, and surgery altogether.
For decades, treatment for stage II and III rectal cancer has relied on those three treatments. They work, but they can leave lasting effects:
- Changes in bowel, bladder, and sexual function
- Infertility
- A higher risk of a second cancer later in life
For people with dMMR/MSI-H tumors, dostarlimab offers a different path, one built around the biology of their cancer. National cancer treatment guidelines (NCCN) already recommended six months of immunotherapy as the preferred approach for dMMR/MSI-H locally advanced rectal cancer; what’s new is that there is now an FDA-approved treatment with a label for this use. The FDA moved quickly on this approval, granting it Breakthrough Therapy and Priority Review status because of how strong the early results were.
What Is the AZUR-1 Trial?
AZUR-1 is the clinical trial the FDA based this approval on, and the results shared in this article come from it. It tested whether dostarlimab alone could clear dMMR/MSI-H rectal cancer so patients could skip chemotherapy, radiation, and surgery.
- Who was in it: 154 adults with stage II or III dMMR/MSI-H rectal cancer who had not yet started treatment.
- What they received: Dostarlimab alone, by IV every three weeks for six months (nine treatments).
- What happened next: Patients whose cancer disappeared were watched closely with regular exams and scans instead of having surgery.
Learn more on ClinicalTrials.gov.
What is dMMR/MSI-H rectal cancer?
About 5–10% of rectal cancers are mismatch repair deficient (dMMR) or microsatellite instability-high (MSI-H). These tumors can’t properly fix mistakes in their DNA, so they build up many genetic changes. Those changes make the tumor easier for the immune system to recognize, which is why immunotherapies like dostarlimab often work so well for this group. dMMR/MSI-H tumors are most common in colorectal, endometrial, and other digestive-tract cancers, but can show up in other solid tumors too.
What do we know, and what are we still learning?
What we know: In the AZUR-1 trial, 71% of patients were treated with dostarlimab alone and needed no further treatment. Among those who had a complete or near-complete response, none have had their cancer return so far (median follow-up about 26 months).
What we’re still learning: This is an accelerated approval, which the FDA grants when early results are strong for a serious condition. We don’t yet know the long-term chance of the cancer returning, because patients haven’t been followed long enough. Results checked by an independent review panel are also still coming in, and continued approval may depend on further study. Full trial results will be presented at the European Society for Medical Oncology (ESMO) Congress in October 2026.
What does this mean for you? The early results are very encouraging, and choosing this path means committing to close, regular check-ups. It’s worth talking with your care team about how to weigh a strong early result while the long-term data continue to mature.
Related reading: Earlier in October 2026, the FDA also approved an immunotherapy combination for stage III dMMR colon cancer. Read our summary: FDA Approval: Immunotherapy for Stage III dMMR Colon Cancer.
Considering This Treatment? Questions for Your Care Team
Choosing a treatment is a decision you and your care team make together. Dostarlimab offers many people with dMMR/MSI-H rectal cancer a real chance to skip chemotherapy, radiation, and surgery. But it’s new, the long-term results are still coming in, and like any cancer treatment it can cause side effects. The best choice for you depends on your biomarker results, your health, and what matters most to you.
These questions can help guide your conversation with your oncologist.
What this treatment could do for me
- How likely is it that dostarlimab alone could clear my cancer?
- How will we know if I’ve had a complete response?
- If the cancer doesn’t fully go away, or comes back, what are my next options?
- We don’t yet know the long-term chance of the cancer returning. How should that factor into my decision?
Side effects and monitoring
- Which side effects are most common, and which are most serious?
- Since this treatment works through my immune system, which symptoms should I report right away? (Immune-related side effects, such as new diarrhea, rash, trouble breathing, or unusual tiredness, can appear suddenly and are easiest to manage when caught early.)
- What tests will you use to check on me during treatment?
- If I have a reaction, would we pause treatment, treat the side effect, or stop?
My life and priorities
- If I don’t have surgery, what will my follow-up visits and scans look like, and for how long?
- Compared with standard treatment, how might this affect my bowel function, sexual health, or fertility?
- How might treatment fit with my work, daily life, and the people who support me?
Getting the full picture
- Does this cancer center have experience treating rectal cancer this way?
- Would a second opinion help before I decide?
- Are there clinical trials I should know about?
There’s no one right answer for everyone. Use these questions to help you and your care team find the path that fits you.
Frequently Asked Questions
What is dostarlimab (Jemperli)?
Dostarlimab is an immunotherapy that helps your immune system find and attack cancer cells. On October 19, 2026, the FDA approved it for adults with stage II or III dMMR/MSI-H rectal cancer.
Is dostarlimab chemotherapy?
No. It’s an immunotherapy, and for this approval it’s given on its own, without chemotherapy or radiation.
How is dostarlimab given for rectal cancer?
In the AZUR-1 trial, patients got dostarlimab by IV every three weeks, for nine treatments over about six months. Your care team will confirm the schedule and dose that’s right for you.
Will I still need surgery?
Maybe not. In the trial, 71% of patients were treated with dostarlimab alone and needed no surgery or other treatment. If the cancer doesn’t fully respond, surgery and other standard treatments are still options.
Who is not eligible for dostarlimab?
Dostarlimab is not approved for rectal tumors that are pMMR/MSS (the large majority), for stage I or stage IV (metastatic) rectal cancer, or for people who have already started chemotherapy, radiation, or surgery. If your biomarker status is unknown, you’d need testing first to find out whether you qualify.
What are the most common side effects?
The most common side effects in the AZUR-1 trial were fatigue, rash, diarrhea, and itchy skin. About 1 in 5 patients had a serious side effect. Because dostarlimab works through the immune system, it can also cause immune-related reactions in various organs, which are most manageable when reported early.
Disclaimer
This article is for educational purposes only and is not medical advice. Treatment decisions should always be made with your own oncology care team.
Sources
- U.S. Food and Drug Administration. “FDA grants accelerated approval to dostarlimab for locally advanced rectal cancer.” October 19, 2026.
- GSK. “Jemperli (dostarlimab-gxly) approved in US as first and only immunotherapy for adults with MSI-H/dMMR locally advanced rectal cancer.” October 19, 2026.
- JEMPERLI (dostarlimab-gxly) Prescribing Information. GSK.
- AZUR-1 trial. “A Study of Dostarlimab in Untreated dMMR/MSI-H Locally Advanced Rectal Cancer.” ClinicalTrials.gov, NCT05723562.
- Cercek A, et al. “PD-1 Blockade in Mismatch Repair–Deficient, Locally Advanced Rectal Cancer.” New England Journal of Medicine. 2022;386:2363-76. doi.org/10.1056/NEJMoa2201445
- Fight Colorectal Cancer. “FDA Approval: Immunotherapy for Stage III dMMR Colon Cancer.” October 12, 2026.
- National Comprehensive Cancer Network (NCCN). NCCN Guidelines for Patients: Rectal Cancer, 2026. nccn.org/patients.