Dr Bekaii-Saab on the Role of Liquid and Tissue Biopsies for Newly Diagnosed GI Cancers

Tanios Bekaii-Saab, MD, FACP, professor of medicine, leader, Gastrointestinal Cancer Program, medical director, Cancer Clinical Research Office, vice chair and section chief for medical oncology, Department of Internal Medicine, Mayo Clinic, highlights the critical role of both liquid and tissue biopsies in the diagnostic and therapeutic planning process for patients with newly diagnosed gastrointestinal (GI) cancers.

For newly diagnosed patients with GI cancer, conducting a comprehensive molecular profile of the tumor is essential, as it informs treatment selection, Bekaii-Saab begins. However, one of the current challenges currently associated with genetic testing is the turnaround time for tissue tests, he continues. Receiving results from a tissue biopsy can take between 3 to 4 weeks, and this testing can also be a challenge if there are difficulties in collecting sufficient and viable tumor samples.

This delay can be problematic, since these results are critical to help drive treatment decisions, Bekaii-Saab explains. However, this is where liquid biopsies, which analyze circulating tumor DNA (ctDNA) in the blood, can play a complementary role, he continues, noting that liquid tests offer a more rapid turnaround time, often within a week. This allows clinicians to gain insights into the genetic landscape of the tumor early in the treatment course, Bekaii-Saab says.

Bekaii-Saab advocates for a dual approach in which both liquid and tissue biopsies are ordered simultaneously at the time of diagnosis. The liquid biopsy can provide preliminary genetic information that may expedite treatment decisions, while the tissue biopsy can serve as a confirmatory test and provide a more comprehensive analysis. If a targetable mutation or relevant biomarker is detected in the liquid biopsy, it is almost certain to be present in the tissue as well, thus accelerating treatment initiation, he notes.

However, if a mutation is not identified in the liquid biopsy, it remains necessary to await tissue biopsy results to rule out the possibility of false negatives, as not all tumor mutations are detectable in the blood due to varying ctDNA shedding patterns among different tumors, he concludes.