From the Research
For individuals at high risk of cancer, the Grail's Multi-Cancer Early Detection test is not recommended as a standard screening tool due to its low sensitivity for early cancer detection, as evidenced by a sensitivity of less than 20% in Stage I disease 1. When considering the choice between Grail's Multi-Cancer Early Detection test and Cancer Guard, it's essential to consult with a healthcare provider who can assess the individual's specific risk factors, family history, and other relevant clinical information. These multi-cancer detection tests are still relatively new, with ongoing research evaluating their sensitivity, specificity, and clinical utility in different populations. They typically work by detecting circulating tumor DNA or other cancer biomarkers in the blood, potentially identifying cancers before symptoms appear. However, it's crucial to understand that these tests should complement, not replace, established screening methods like mammography, colonoscopy, or low-dose CT scans, which have proven benefits for specific cancer types. Any positive result from these multi-cancer screening tests would require follow-up diagnostic testing to confirm the presence of cancer. A recent systematic literature review highlighted the variability in sensitivity and specificity among different multi-cancer early detection tests, including Grail's Galleri test, with sensitivity ranging from 20.8-66.3% and specificity from 98.4-99.5% 2. Given the limited evidence and high risk of bias in most studies, further research is needed to determine the clinical utility of these tests in real-world settings. In the context of real-life clinical medicine, a cautious approach is warranted, prioritizing established screening methods and considering multi-cancer detection tests as adjunctive tools under the guidance of a healthcare provider. The most recent and highest quality study available, a 2025 systematic literature review, supports this approach by highlighting the need for more research on patient-relevant outcomes and the potential harms and benefits of these tests 2.