Two New Immunotherapy Approvals for Colorectal Cancer
This October, the U.S. Food and Drug Administration (FDA) approved two immunotherapy treatments for colorectal cancer that has not spread to distant parts of the body. Immunotherapy helps your own immune system find and fight cancer. Both approvals are for tumors with a feature called mismatch repair deficiency (dMMR), also known as microsatellite instability high (MSI-H). In these tumors, the system that fixes mistakes in DNA is broken, which makes the cancer easier for the immune system to spot. Only a small share of colorectal cancers have this feature, and the only way to know is to test the tumor.
The first approval adds atezolizumab to chemotherapy after surgery for stage III dMMR colon cancer. The second allows dostarlimab, given on its own, for stage II or III dMMR/MSI-H rectal cancer. Here is who each treatment is for, what the studies found, and what the results do and do not tell us.
Atezolizumab: Immunotherapy Joins Chemotherapy After Surgery
The indication: On October 8, 2026, the FDA approved atezolizumab (Tecentriq) for adults and children age 2 and older with stage III colon cancer that is dMMR. Stage III means the cancer has reached nearby lymph nodes but not distant organs. Atezolizumab is given after surgery, together with standard chemotherapy that includes oxaliplatin, to lower the chance the cancer comes back. Treatment lasts a year: six months of atezolizumab plus chemotherapy, then six months of atezolizumab alone. Atezolizumab can be given by IV, or as a shot under the skin for patients 12 and older who meet body weight requirements.
What the study found: The approval is based on a large clinical trial called ATOMIC, which included 712 people whose stage III dMMR colon cancer had been fully removed by surgery. Patients were randomly placed in one of two groups: one got standard chemotherapy alone, and the other got the same chemotherapy plus atezolizumab. People who got atezolizumab were half as likely to have their cancer come back or to die during the study. The lead researcher, Dr. Frank Sinicrope, reported that the benefit was seen regardless of age, sex, race, or how far the tumor had grown.
What it means: If you have stage III colon cancer that tests positive for dMMR, there is now an approved treatment that lowers your risk of the cancer returning more than chemotherapy alone. Because ATOMIC compared the two approaches directly in a large group of patients, the results are considered strong, and experts expect this to become the new standard treatment for this group.
What it does not mean: This approval covers colon cancer only, not rectal cancer, and only tumors that are dMMR. It does not apply to stage II colon cancer or to the roughly 85% of colon cancers that are not dMMR. Atezolizumab does not replace chemotherapy; the two are given together. Researchers also need more time to learn whether adding atezolizumab helps people live longer overall, not just stay cancer-free longer.
Dostarlimab: A Path That May Skip Chemotherapy, Radiation, and Surgery
The indication: On October 19, 2026, the FDA approved dostarlimab (Jemperli) for adults with stage II or stage III rectal cancer that is dMMR/MSI-H and has grown in or near the rectum but not spread to distant organs (called locally advanced). The tumor's dMMR/MSI-H status must be confirmed with an FDA-authorized test. Dostarlimab is given alone, by IV, every three weeks, for up to nine doses, or about six months. It is the first immunotherapy approved in the U.S. for these patients.
What the study found: The approval is based on a study called AZUR-1, which included 154 people who had not yet had any treatment for their rectal cancer. Everyone in the study received dostarlimab. About two years later, 71% had needed nothing else: no surgery, no chemotherapy, and no radiation, and their cancer had not grown. Nearly half of the patients reviewed by independent experts showed no sign of the tumor on exams and scans for at least a full year, and many more had the same result but had not yet been followed that long. An earlier, smaller study of 50 patients at Memorial Sloan Kettering Cancer Center found that 93% had no sign of cancer for at least a year.
What it means: The usual treatment for this kind of rectal cancer combines chemotherapy, radiation, and surgery. These can cause lasting problems with bowel, bladder, and sexual function, and some people need a permanent ostomy. For people with dMMR/MSI-H rectal cancer, dostarlimab offers a real chance to avoid those treatments and keep the rectum. People whose tumors disappear still need close checkups, with scope exams and MRI scans every four months for the first two years and every six months after that.
What it does not mean: This is an accelerated approval, which means the FDA approved dostarlimab based on early results. Keeping the approval may depend on longer follow-up confirming the benefit. Because everyone in AZUR-1 got dostarlimab, the study cannot show exactly how it compares with standard treatment. Dostarlimab does not work completely for everyone: about 1 in 4 patients still needed surgery or other treatment. The approval also does not cover rectal cancers that are not dMMR/MSI-H, which are most rectal cancers.
Both Start With One Test
Neither treatment is an option unless you know whether your tumor is dMMR/MSI-H. If you have been diagnosed with colorectal cancer, ask your care team whether your tumor has been tested, and what the result means for your treatment. These are U.S. approvals. Whether and when they become available in other countries depends on each country's health regulators, and several are already reviewing them through an FDA program called Project Orbis.
Learn more about mismatch repair deficiency, microsatellite instability, and biomarker testing at KnowYourBiomarker.org. Know Your Biomarker is an awareness, education, and advocacy program promoting global access to colorectal cancer biomarker testing.