This week, I’ve been looking at the results of the phase 3 ATOMIC trial, which tested the addition of adjuvant or after surgery immune checkpoint therapy to chemo for stage 3 colorectal cancers with DNA mismatch repair mutations. The investigators found that adding the immunotherapy atezolizumab, an anti-PDL1 drug, had a disease-free survival of 86.3% after three years compared to 76.2% for chemotherapy alone.
This is an advance for patients with this colorectal cancer subtype, which represents about 10-15% of non-metastatic colon cancer, and it’s also more evidence that tumors with these particular mutations are especially vulnerable to immune checkpoint therapy. Last year, Memorial Sloan Kettering scientists showed that anti-PD1 therapy alone could achieve complete responses in 100% of early-stage dMMR rectal cancer patients before surgery. In the follow-up to that, the trial showed that 35 of 54 non-rectal cancer patients achieved a complete response.
To me, this raises some interesting questions for colorectal patients who fall into this category. Given what we’ve seen thus far, you have to wonder if the strategy is to move all non-metastatic dMMR colorectal cancer patients to neoadjuvant immunotherapy, rather than waiting to give it after surgery. ATOMIC doesn’t answer this, but perhaps future studies will.
Next week, I’ll be traveling to San Diego for AACR, so say hi if you see me around! We’ll be running our usual pop-up newsletter, AACR in 30 seconds, and you can sign up for that here.
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