Earlier Detection of Relapse in Colorectal Cancer

Blase Polite, MD: The [Tenna] Henriksen study published in JCO [Journal of Clinical Oncology] in 2021 is a sample of 265 patients with stage II and III colon cancer who underwent resection. It looked at the predictive and prognostic value of a positive ctDNA [circulating tumor DNA] postoperatively. First, the overall data: about 9% of patients had ctDNA positivity postoperatively; 75% of those patients relapsed. The 25% who didn’t relapse received adjuvant chemotherapy. That’s important because, from a hypothesis-generation standpoint, it begins to say that there are patients who are ctDNA positive, and if we give them chemotherapy, we can convert them to ctDNA negative and perhaps decrease the chance of a relapse.

All patients who did not relapse got adjuvant chemotherapy, but many who got adjuvant chemotherapy did relapse, so it’s not perfect. Adjuvant chemotherapy does not reduce the risk to 0, but some portion of patients benefit from it. When you compare that with the ctDNA-negative patients, 13.6% of them relapsed, but there’s about a 75% relapse in the ctDNA-positive patients. Those are very large differences between ctDNA positive vs negative. If you look at ctDNA positivity vs ctDNA consistent negativity at any point over a 2-year period, patients who are ctDNA positive have a 36 times higher risk of relapse compared with those who remain negative. There’s no question that we’ve found 1 of our most powerful prognostic factors in predicting colon cancer relapse. We’ve identified the best way to detect which patient population will relapse. We don’t know if we can benefit the patients who are ctDNA positive by giving them more aggressive chemotherapy. Alternatively, can we choose not to treat patients who are ctDNA negative? The predictive nature of the assay remains to be seen, but I’m very excited to say that there are worldwide efforts to try to answer that question.

Transcript edited for clarity.