Galleri Test: Promise and Pitfalls of a New Era in Cancer Screening
- Saneka Chakravarty, MD, FACC
- Jul 23
- 3 min read
Updated: Jul 31
Are you familiar with the Galleri test?
This blood test is created to examine cell-free DNA methylation patterns to detect signals linked to more than 50 types of cancer. It marks a revolutionary step forward in cancer detection technology.
Who Is Eligible for the Galleri Test?
As of now, eligibility criteria typically include:
1. Age
Adults aged 50 or older are the primary group the test is recommended for.
This is because cancer risk increases significantly with age.
2. Younger Adults (Aged 40–49)
May be eligible if they are at elevated risk of cancer, such as:
Family history of cancer
Genetic predisposition (e.g., BRCA mutations)
Smoking history
Other environmental or lifestyle risk factors
3. Asymptomatic Individuals
The Galleri test is intended for people without current symptoms of cancer.
It is not a diagnostic test or a replacement for standard screening (like mammograms, colonoscopies, or Pap smears).
4. Not for People with Active Cancer
It’s not designed for people currently undergoing cancer treatment or those who have had cancer recently (depending on provider guidance).
Important Notes:
The Galleri test requires a prescription from a healthcare provider.
It is not covered by most insurance plans as of now and is considered a supplemental screening tool.
Cost is typically around $950 USD, but may vary.
How Does Galleri Perform?
Scientific evidence shows that Galleri has very high specificity (98.4–99.5%), meaning that false positives are rare. However, its sensitivity is variable, ranging from 20.8% to 66.3%, with lower sensitivity for early-stage cancers (Stage I–II) and higher sensitivity for later-stage cancers (Stage III–IV).
This pattern suggests that while the test is unlikely to wrongly signal cancer when none is present, it may miss a substantial proportion of early cancers—precisely the ones where early detection could make a curative difference.[¹][²]
What Does the Evidence Say?
To date, studies of Galleri have largely been case-control or cohort studies—most often conducted in populations with already known cancers. This design may overestimate how well the test performs compared to how it would function in real-world screenings of asymptomatic individuals.
Crucially, there are no completed randomized controlled trials (RCTs) that show Galleri can reduce cancer-specific or all-cause mortality. Therefore, its clinical utility in the general population remains unproven. However, large-scale trials, including the NHS-Galleri trial and NCI-led studies, are ongoing to answer these critical questions.[³][⁴][²]
Potential Risks and Limitations
Despite its promise, the Galleri test carries several notable limitations:
Overdiagnosis: Detecting cancers that may never become clinically significant
False reassurance: A false-negative result may delay appropriate diagnosis or care
Downstream harms: Unnecessary follow-up testing, anxiety, or invasive procedures
High cost: At approximately $950 per test, affordability and equitable access are major concerns, especially if considered for large-scale population use in the U.S.[⁵][⁴]
Conclusion
In summary, Galleri is a promising innovation in the realm of cancer screening—but its current role is investigational. While it boasts excellent specificity, its modest sensitivity for early-stage cancers, uncertain mortality benefit, and significant cost and implementation challenges all warrant caution.
Ongoing randomized controlled trials are essential to determine whether Galleri—and other MCED tests—can truly improve cancer outcomes at the population level in the United States.
What do you think? Is this a test you would opt for?
Yes
No
Yes if the cost was lower
References
1. Multi-Cancer Early Detection Tests for General Population Screening: A Systematic Literature Review. Wade R, Nevitt S, Liu Y, et al. Health Technology Assessment (Winchester, England). 2025;29(2):1-105. doi:10.3310/DLMT1294.
2. Circulating Tumor DNA (ctDNA): Can It Be Used as a Pan-Cancer Early Detection Test?. Duffy MJ, Crown J. Critical Reviews in Clinical Laboratory Sciences. 2024;61(4):241-253. doi:10.1080/10408363.2023.2275150.
3. Cell-Free DNA-Based Multi-Cancer Early Detection Test in an Asymptomatic Screening Population (NHS-Galleri): Design of a Pragmatic, Prospective Randomised Controlled Trial. Neal RD, Johnson P, Clarke CA, et al. Cancers. 2022;14(19):4818. doi:10.3390/cancers14194818.
4. Assessing the Clinical Utility of Liquid Biopsies Across 5 Potential Indications From Therapy Selection to Population Screening: A Review. Carr DJ, Welch HG. JAMA Internal Medicine. 2023;183(10):1144-1151. doi:10.1001/jamainternmed.2023.3603.
5. Multi-cancer early detection screening tools: A dream come true or a nightmare in the offing. Leonard M Fleck and Aakash Dave. Journal of Clinical Oncology. 2023;41(Suppl 16):e18926. doi:10.1200/JCO.2023.41.16_suppl.e18926.
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