Aparna Parikh, MD, MS, talks about the MD Anderson INTERCEPT program, which is studying the relationship between ctDNA and recurrence in colorectal cancer.
Tanios S. Bekaii-Saab, MD: Aparna, tell us more about this effort at [The University of Texas] MD Anderson [Cancer Center], the INTERCEPT program.
Aparna Parikh, MD, MS: This abstract at ASCO [American Society of Clinical Oncology Annual Meeting] has been nagging me. It calls into question what MRD [minimal residual disease] truly is. As we have been talking about, not all of us necessarily without talking to our patients or doing routine surveillance, the INTERCEPT integrated MRD testing into routine colorectal cancer clinical care. [MD Anderson] did this for several years, and they did this for all stages except for stage I. They had routine surveillance visits, including scans and tumor markers, according to NCCN [National Comprehensive Cancer Network] Guidelines. Then they added ctDNA [circulating tumor DNA] testing to each surveillance visit. They did that testing every 3 months as part of their program across the center, in over 1000 patients.
What I found interesting was the number of patients who were positive but were actually metastatic when you looked. I believe 53% of patients were positive but had radiographic findings of metastatic disease. It’s making us think about what ctDNA testing is. With the available test, can we know if this is metastatic disease that you’re detecting? Is there a narrow window where it’s truly minimal residual disease, or have you hit the threshold of metastatic disease? With newer tests, can we shift so you’re detecting things early? It’s a great initiative. With over 50% metastatic with a positive test, it’s going to be challenging for trials. We’ll talk a little about a trial that I’m running. It’s something that we’re seeing: by the time you’re positive on the commercially available test with the current sensitivities, you’re already metastatic.
Tanios S. Bekaii-Saab, MD: That’s interesting. We’re confirming metastatic disease in a patient where radiographically we weren’t able to measure this.
Transcript edited for clarity.