Genentech: FDA approves Tecentriq plus fluoropyrimidine and oxaliplatin as adjuvant for stage III dMMR colon cancer

Regulatory decision and clinical impact

The FDA approved Tecentriq (atezolizumab) in combination with a fluoropyrimidine and oxaliplatin as an adjuvant treatment for stage III deficient DNA mismatch repair (dMMR) colon cancer. The decision establishes the first approved immunotherapy‑based adjuvant regimen for this subset and is Tecentriq's twelfth U.S. indication.

ATOMIC trial evidence

The approval rests on the Phase III ATOMIC study (A021502), which enrolled 712 patients and randomized them 1:1. ATOMIC showed that adding Tecentriq to modified FOLFOX6 (folinic acid, fluorouracil and oxaliplatin) reduced the risk of disease recurrence or death by 50% versus chemotherapy alone. The 36‑month disease‑free survival was 86% with the combination compared with 76% with mFOLFOX6 alone. Patients received mFOLFOX6 plus Tecentriq for 12 cycles (six months) followed by Tecentriq monotherapy for 13 cycles (an additional six months). Efficacy was determined using immunohistochemistry for mismatch repair status, such as the VENTANA MMR RxDx Panel, and the safety profile matched prior experience with Tecentriq and mFOLFOX6.

Disease context

Colon cancer is common and lethal: nearly 25% of cases present at stage III and about 30% of stage III patients recur within five years despite surgery and chemotherapy. Approximately 15% of colon cancers are dMMR/MSI‑H, a biology associated with higher mutation rates and potential sensitivity to immunotherapy—supporting the rationale and clinical benefit observed in ATOMIC.