Liquid Biopsy for Early Cancer Detection

Oct 18, 2022

People want to detect cancer because cancer comes in a close second as a leading cause of death in the US. The federal government has made cancer detection and treatment a high priority with their Cancer Moonshot program. While cancer treatments have come a long way, prolonging life and improving quality of life, the ideal situation still involves catching it early. Primary care physicians usually reference recommendations put forward by the US Preventive Services Task Force. Currently, the only screening recommendations backed by the most rigorous studies, earning them an A or B rating, are for cervical, breast, lung, and colorectal cancer. These screening tests involve fairly invasive approaches to catch cancer early by imaging or by direct visualization and sampling. Many patients raise a valid question, “Why can’t there just be a blood test to check for cancer?” Some cancers do have blood-based biomarkers such as the PSA, which previously was widely used to screen for prostate cancer, but now has a much weaker recommendation. Other blood tests exist as cancer treatment tracking markers, but do a poor job as screening markers.

The field of multi-cancer early detection (MCED) seeks to fundamentally upset the current paradigm. Instead of looking at unique proteins, most researchers study the DNA which cancer cells spill into the bloodstream, aptly named circulating tumor DNA (ctDNA). The science behind MCED is incredibly complicated and involves not just high-level biochemistry, but also extensive machine learning to study patterns which cancer DNA exhibits. Currently, the only commercially available MCED product is the Galleri test produced by Grail. Peter Attia has a great episode on the history and background of this field and wrote an article a year ago on the Grail test. HLTH also had a panel discussion on the clinical use of the Galleri test.

I met Dr. Jeff Venstrom, the CMO of Grail, last month in DC and he was kind enough to do an interview with me where we explore the MCED field and all the work and due diligence behind the Galleri test. Dr. Venstrom is an oncologist who received his medical degree from Vanderbilt University and completed residency at Johns Hopkins followed by fellowship at Memorial Sloan Kettering.