More than 1.9 million peopleTrusted Source around the world were diagnosed with colorectal cancer each year, making it the third most common cancer globally.
Also known as colon cancer, this type of cancer is currently treated in a number of ways, including surgery, radiation therapy, immunotherapy, and chemotherapy.
However, not all treatments work for all types of colorectal cancer. For example, deficient mismatch repair (dMMR) colon cancerTrusted Source, which is caused by mutations in genes that correct mistakes that happen when a person’s DNA is copied, encompasses 5-15% of colorectal cancer cases and may not be as responsive to chemotherapy as other types.
Now, a new study presented at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting reports that adding immunotherapy to chemotherapy after surgery for stage 3 colon cancer may help decrease a person’s recurrence and death rate by half.
The findings are yet to be published in a peer-reviewed journal.
What is atezolizumab?
For this phase III clinical trial, researchers recruited 712 people with an average age of 64 who had dMMR stage 3 colon cancer. This stage of colorectal cancer occurs when the cancer spreads to the body’s lymph nodes, but nowhere else.
All study participants had undergone surgery to have their cancer removed and still had cancer cells in their lymph nodes.
Participants were randomly assigned to either receive just mFOLFOX6Trusted Source chemotherapy for colorectal cancer, or mFOLFOX6 plus an immune checkpoint inhibitorTrusted Source called atezolizumabTrusted Source.
Atezolizumab targets a specific protein in cancer cells called programmed death-ligand 1 (PD-L1)Trusted Source. PD-L1’s job is to keep cancer cells “hidden” from detection by the body’s immune system. By binding and blocking to PD-L1, atezolizumab makes the cancer cells “visible” to the immune system so it can attack them.
At the study’s conclusion, researchers found that participants receiving chemotherapy with immunotherapy had a 50% decrease in cancer recurrence and death — known as disease-free survival (DFS) — compared to those who only received chemotherapy.
“The findings from our study represent a major advance in the adjuvant treatment of dMMR stage 3 colon cancer and will now change the treatment for this type of cancer,” says Frank Sinicrope, MD, oncologist at the Mayo Clinic in Minnesota and lead author of this study, in a press release.
“It’s extremely rewarding to be able to offer our patients a new treatment regimen that can reduce the risk of recurrence and improve their chances of survival,” he says.
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