A Note from Our Physicians
You may have seen recent news articles about an update from GRAIL regarding the large NHS study of the Galleri blood test for early cancer detection in the United Kingdom. We want to share our perspective.
Galleri is a promising new technology with an ambitious goal: to detect certain cancers earlier when treatment may be more effective. The Galleri test is a blood-based multi-cancer early detection (MCED) test that analyzes cell-free DNA methylation patterns to screen for more than 50 different cancer types simultaneously in asymptomatic adults. The test uses machine learning algorithms to detect cancer signals and predict the anatomical origin of the cancer to guide diagnostic workup.
As with any new test, well-designed randomized controlled trials are essential to determine who is most likely to benefit, how the test should be used, and what its true strengths and limitations are. The National Health Service (NHS) in England just completed a large well designed trial:
- 142,000 participants were enrolled in the study from ages 50-77.
- Participants had no cancer symptoms and had not had cancer or cancer treatment in the three years prior to enrollment in the study.
- The study ran for three years and involved annual blood tests with the goal of producing a significant reduction in advanced cancers.
While preliminary reports from the NHS study have been described in the media as less encouraging than hoped, it is important to reserve firm conclusions until the full data are published in peer-reviewed scientific journals. Headlines and press releases often lack the detail needed to properly interpret results, including how the study was designed, which cancers were evaluated, and how outcomes were measured. Even if the overall results did not meet its primary goal, it is possible that this test will prove to be a useful screening tool for certain groups of patients based on age or certain risk factors for cancer.
As your physicians, our role is to weigh the potential benefits and limitations of any screening test—considering factors such as accuracy, false positives and negatives, downstream testing, possible harms, and overall clinical value. We will review the full study results carefully when they become available and integrate that evidence into our recommendations going forward.
