Grail's Multi-Cancer Blood Test Faces Crucial FDA Review

An emerging approach to cancer screening, Grail Inc.'s Galleri blood test, designed to detect signs of multiple cancers in apparently healthy individuals, is undergoing a significant regulatory review by U.S. government advisers. The test, which looks for DNA fragments shed by tumor cells, aims to offer a single-draw screening method for various cancers, a departure from current single-cancer tests like mammograms and colonoscopies.

A panel of Food and Drug Administration advisers is scheduled to vote on whether the proposed benefits of the Galleri test, intended for individuals aged 50 and older, outweigh potential risks such as missed diagnoses or false alarms. FDA staff, in documents released prior to the meeting, indicated no major safety concerns but sought discussion on the test's efficacy in detecting early-stage cancers for marketing purposes.

While individuals in the U.S. can already purchase the test out-of-pocket, typically for over $700, FDA approval could significantly broaden its availability by enabling coverage from Medicare and private insurers. Oncologists, however, express divided opinions on its readiness for widespread adoption. Some acknowledge the technology's promise but caution that a positive signal necessitates further, potentially costly, diagnostic tests that may not yield definitive answers.

Concerns have been raised regarding the test's data and methodology. The FDA considers the current version of the test distinct from the one used in pivotal studies. To address this, Grail re-tested frozen blood samples from study participants with its newer Galleri test. Furthermore, the company's submission to the FDA includes only the first year of data from its primary study, a 140,000-person trial conducted in the U.K. This study did not meet its main objective of demonstrating a statistically significant reduction in late-stage cancers, a detail anticipated to be a point of discussion.

In the data presented to the FDA, Grail's test reportedly predicted cancer in over 66% of patients flagged with a "cancer signal detected." Within the one-year study period, the test identified approximately 30% of cancers that were later confirmed by physicians. The study, a collaboration with the U.K.'s National Health Service, was not designed to prove that Galleri screening reduces cancer mortality, which would require a longer follow-up period.

An analysis of a separate U.S. study showed the test detected a cancer signal in 287 individuals, with cancer being diagnosed in 173 of them. The test demonstrated greater effectiveness in detecting less common cancers, such as liver and ovarian cancers, compared to more prevalent forms like prostate cancer. This variability raises questions about its potential broad impact if deployed for millions of Americans.

One significant concern is that individuals receiving a negative result from the DNA test might forgo routine, guideline-recommended screenings like mammograms or colonoscopies. Experts emphasize the importance of physicians and patients understanding both the advantages and limitations of such tests if cleared by the FDA. Key questions remain about the optimal screening frequency and the long-term effectiveness of the test in catching cancers early.