Atezolizumab plus chemo won FDA approval for some Stage III colon cancers

On Oct. 8, 2026, the Food and Drug Administration approved atezolizumab, sold as Tecentriq by Genentech, together with chemotherapy for adults and children as young as two with Stage III colon cancer whose tumors are mismatch repair deficient, abbreviated dMMR. The approval is narrow by design: it covers only that molecular subtype, not Stage III colon cancer as a whole.

The decision arrived a day before the October 9 date the agency had set when it granted priority review, and it rests on a single randomized trial in which adding the immunotherapy to standard chemotherapy cut the risk of recurrence or death by half.

The dMMR Population the Approval Covers

According to the FDA’s approval notice, atezolizumab is indicated with a fluoropyrimidine and oxaliplatin as adjuvant treatment, meaning therapy given after surgery, for Stage III dMMR colon cancer in patients two years of age and older. Tumors that are mismatch repair deficient cannot fix copy errors in their DNA, accumulate many mutations and tend to be visible to the immune system, which is the biological reason a checkpoint inhibitor is tested there. Roche, Genentech’s parent company, has said about 15 percent of colon cancer patients have dMMR or MSI-H tumors.

The agency also approved Tecentriq Hybreza, a subcutaneous formulation that combines atezolizumab with hyaluronidase, for patients 12 and older who weigh at least 40 kilograms. The Hybreza dose is a single 15 mL injection every three weeks, delivering 1,875 mg of atezolizumab, alongside chemotherapy for six months and then alone for six more.

ATOMIC, the Trial Behind the Decision

The evidence comes from ATOMIC, also labeled A021502, a multicenter, open-label study that enrolled 711 adults and one pediatric patient with Stage III dMMR colon cancer after complete surgical removal of the tumor, per the FDA. Patients were randomized one to one. One arm received atezolizumab with mFOLFOX6 chemotherapy for 12 cycles and then atezolizumab alone for six months; the other received mFOLFOX6 for 12 cycles. The primary endpoint was disease-free survival as judged by investigators.

The FDA reports a hazard ratio of 0.50 for disease-free survival (95 percent confidence interval 0.35 to 0.73, p = 0.0001), with median disease-free survival not reached in either arm. The National Cancer Institute sponsored the study, and the Alliance for Clinical Trials in Oncology ran it with Genentech and Germany’s AIO group, according to Genentech’s priority review announcement. The same release put 36-month disease-free survival at 86 percent with atezolizumab and 76 percent with chemotherapy alone, and noted publication in the New England Journal of Medicine.

Dr. Frank Sinicrope, the lead author, presented the first results at the 2025 American Society of Clinical Oncology meeting. In OncLive’s account of that briefing, he said the data “establish this combination as a new standard treatment for patients with stage III colon cancer and dMMR.” Three-year disease-free survival there was 86.4 percent versus 76.6 percent, and the reported safety cost was a manageable increase in nonfebrile neutropenia.

Priority Review and the Project Orbis Track

Genentech announced on June 10 that the FDA had accepted its supplemental application with priority review and a decision target of Oct. 9. In its release, Levi Garraway, Genentech’s chief medical officer, said the ATOMIC results show the regimen “can substantially reduce the risk of disease recurrence or death.” Roche’s companion statement carried a figure from Michael Sapienza, chief executive of the Colorectal Cancer Alliance: one in three patients with Stage III colon cancer relapses within five years.

The review ran under Project Orbis, the Oncology Center of Excellence framework that lets partner regulators assess a cancer drug at the same time as the FDA. The FDA notice lists concurrent reviews at Australia’s Therapeutic Goods Administration, Health Canada, Israel’s Ministry of Health and Switzerland’s Swissmedic, all still ongoing as of the approval date. Genentech also submitted an Assessment Aid, a voluntary document that organizes the application for reviewers.

Warnings and Dosing on the Tecentriq Label

The FDA lists immune-mediated adverse reactions, infusion-related reactions, complications of allogeneic stem-cell transplantation and embryo-fetal toxicity among the warnings. Adults receive 840 mg every two weeks, 1,200 mg every three weeks or 1,680 mg every four weeks with chemotherapy for six months, then atezolizumab alone for another six months or until recurrence or unacceptable toxicity. Children get weight-based doses of 10 mg per kilogram every two weeks or 15 mg per kilogram every three weeks, capped at 840 mg and 1,200 mg respectively.

Full prescribing information for both products is to be posted on Drugs@FDA. The label as approved, not the trial publication, will govern how oncologists select patients, and the FDA notice ties eligibility to a confirmed dMMR result on the tumor. Patients whose Stage III tumors are mismatch repair proficient, the large majority of colon cancers, fall outside the indication, which is why the approval applies to some Stage III colon cancers and not to the stage in general. The FDA notice counts one pediatric participant among the 712 patients randomized in ATOMIC, against 711 adults.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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