Tecentriq (atezolizumab) + mFOLFOX6 for stage III dMMR colon cancer: ATOMIC trial results

The New England Journal of Medicine published results of the phase III ATOMIC trial in patients with completely resected stage III colon cancer with mismatch repair deficiency (dMMR). The trial compared standard adjuvant mFOLFOX6 with the addition of Tecentriq (atezolizumab) versus mFOLFOX6 alone.

Key trial data

• 712 patients were randomized: 355 to Tecentriq (atezolizumab) + mFOLFOX6 and 357 to mFOLFOX6 alone
• Median follow-up was 40.9 months
• 3-year relapse-free survival was 86.3% in the atezolizumab group vs 76.2% in the chemotherapy-only group
• Adding Tecentriq (atezolizumab) reduced the risk of relapse or death by 50% (HR 0.50; p<0.001)
• This is a highly significant result for adjuvant therapy in microsatellite unstable stage III colon cancer

Clinical significance

For dMMR colon tumors, immunotherapy has long demonstrated high activity in metastatic disease. But in the adjuvant setting -- after radical surgery for stage III disease -- convincing data had not previously existed.

Now, for stage III patients with microsatellite instability after surgery, the discussion must include not only standard adjuvant chemotherapy but also the question of adding Tecentriq (atezolizumab). This takes into account not just the stage but also the biology of the tumor.

Limitations

The trial applies only to stage III disease and only to tumors with high microsatellite instability after complete resection. These data do not apply to standard, so-called microsatellite stable tumors, nor to metastatic disease.

In the trial, mFOLFOX6 remained the backbone of treatment, with Tecentriq (atezolizumab) added to it. Additionally, toxicity in the combination group was higher.

When a second opinion is helpful

• If you have stage III colon cancer after surgery and adjuvant therapy is being discussed
• If the discharge summary does not contain a clear microsatellite instability (MSI) result
• If standard chemotherapy is being proposed without discussion of the role of immunotherapy
• If physicians disagree about the applicability of these data to your case

What to prepare for consultation

• Histopathology report
• MSI testing results
• Postoperative discharge summary
• Pathological staging (pT and pN)
• CT scans performed before and after surgical treatment
• Complete blood count and biochemistry panel
• List of comorbidities and current medications

Frequently asked questions

Source

NEJM: Atezolizumab plus FOLFOX for Stage III Mismatch Repair-Deficient Colon Cancer