AACR, Author Interviews, Biomarkers, Chemotherapy, Colon Cancer, MD Anderson / 10.11.2015
Plasma cfDNA Can Monitor Response To Metastatic Colon Cancer Treatment
MedicalResearch.com Interview with:
Van K. Morris, M.D.
Assistant Professor, GI Medical Oncology
University of Texas – M.D. Anderson Cancer Center
Houston, TX 77030
Medical Research: What is the background for this study? What are the main findings?
Dr. Van K Morris: BRAF V600E mutations are associated with poor clinical outcomes for patients with metastatic colorectal cancer. Patients were enrolled in a phase I clinical trial with the BRAF inhibitor vemurafenib, the anti-EGFR antibody cetuximab, and irinotecan. Blood samples were collected every two weeks with each dose, and plasma was analyzed for changes in the fraction of mutant BRAF V600E allele relative to wild-type BRAF allele with time. Trends in circulating free DNA (cfDNA) changes were compared with radiographic changes by RECIST 1.1 criteria to examine this technique as a marker for response to therapy.
For patients who had a response radiographically, drastic reductions in the BRAF V600E allele fraction were observed even after two weeks of starting therapy, well before the first restaging scan. Patients who did not have responses radiographically had less dramatic changes relative to baseline in the BRAF V600E allele fraction. This technique analyzing cfDNA from plasma was validated using two different approaches – digital droplet PCR and next-generation sequencing by Guardant Health. Sequencing of cfDNA was also compared in pretreatment and post-progression samples, and novel mutations in MEK1 and GNAS were observed uniquely in post-progression samples.
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