Multicancer Blood Test Detects 17 Cancer Types In Large Prospective Study

By Julie Ferris-Tillman, Ph.D.

 A large prospective study published today in Nature Medicine found that a blood test designed to detect multiple cancers identified cancer signals across 17 broad cancer types, such as ovarian, lung, breast and colorectal cancers, and many which do not have recommended screening tests.

Mayo Clinic was among the institutions participating in the prospective, interventional study, which enrolled 35,878 adults age 50 and older. Karthik Giridhar, M.D., a Mayo Clinic medical oncologist, was a study investigator and senior author.

The multicancer early detection (MCED) test analyzes small fragments of DNA that cells release into the bloodstream. Researchers use patterns in these fragments to detect signals associated with cancer. When a cancer signal is detected, the test also predicts the likely location of the cancer to help physicians determine appropriate follow-up testing.

Among 32,007 participants included in the study’s performance analysis, 287 had a positive MCED test result. Cancer was diagnosed in 173 of those participants. The test had a positive predictive value of 60.3% and specificity of 99.64%. Among participants with a true-positive result, the test correctly predicted one of the two most likely cancer signal origins in 91.3% of cases.

“One of the challenges in cancer screening is that most cancers do not have an established screening test,” says Dr. Giridhar. “This study helps us better understand how a multicancer blood test might complement existing screening approaches by identifying cancer signals that otherwise may not be detected through routine screening.”

Researchers found that 72.8% of cancers detected by the MCED test were cancer types without U.S. Preventive Services Task Force grade A or B screening recommendations. Among the 151 participants with at least one newly diagnosed primary cancer detected by the test, 53% had stage 1 or 2 disease and 70.9% had stage 1, 2 or 3 disease.

Giridhar also notes that these tests are not yet a substitute for established cancer screenings. Instead, they may supplement existing screening approaches and help expand understanding of cancer detection.

PATHFINDER 2 was a single-arm study, and its endpoints were descriptive, with no comparator group or formal hypothesis testing. The authors say randomized trials and further follow-up are needed to determine the clinical utility of MCED testing in routine clinical practice. The study also used an earlier version of the test that has since been replaced by a commercially available version.

The study was designed and funded by GRAIL Inc., which also participated in data analysis and interpretation and preparation of the manuscript. Dr. Giridhar reports consulting and advisory relationships with GRAIL and other organizations and travel expenses from GRAIL. A complete list of author disclosures is included in the published study.