Guidelines for Using the Galleri Test for Cancer Screening
The Galleri test is an emerging multi-cancer early detection (MCED) test that is still under clinical investigation and is not currently recommended in any established cancer screening guidelines.
What is the Galleri Test?
The Galleri test is a blood-based screening test that uses cell-free DNA technology to detect multiple types of cancer simultaneously in asymptomatic individuals. Key features include:
- Designed to detect approximately 50 different cancer types 1
- Uses circulating tumor DNA (ctDNA) as a biomarker 2
- Shows high specificity (>99%) in preliminary studies 2
- Sensitivity varies by cancer type and stage, generally lower for early-stage disease 2
Current Status of Galleri in Guidelines
No major medical organizations or cancer screening guidelines currently recommend the Galleri test as part of routine cancer screening. The test is still being evaluated in clinical trials to determine its clinical utility.
Ongoing Clinical Evaluation
The NHS-Galleri trial is the largest current evaluation of this technology:
- Large randomized controlled trial in England 3
- Enrolled over 140,000 participants aged 50-77 years 3
- Participants must be:
- 50-77 years old
- ≥3 years without cancer diagnosis or treatment
- Not undergoing investigation for suspected cancer 3
- Primary objective: Demonstrate reduction in stage III and IV cancer incidence in the intervention versus control arm 3-4 years after randomization 3
Potential Advantages and Limitations
Advantages:
- Ability to detect multiple cancer types with a single blood test 2
- High specificity in preliminary findings (>99%) 2
- Potential to detect cancers that currently lack established screening programs 4
Limitations:
- Limited sensitivity for early-stage cancers 2
- Most published studies are case-control investigations with known cancer patients rather than true screening populations 2
- Actual performance in asymptomatic screening populations may differ from reported values 2
- Clinical utility (reduction in cancer mortality without excessive overdiagnosis) not yet established 2
Current Established Cancer Screening Guidelines
While waiting for evidence on the Galleri test, patients should continue to follow established cancer screening guidelines:
- Breast cancer: Annual mammography starting at age 40 5
- Colorectal cancer: Multiple options starting at age 50, including:
- Annual fecal occult blood test (FOBT)
- Flexible sigmoidoscopy every 5 years
- Colonoscopy every 10 years
- CT colonography every 5 years 5
- Cervical cancer: Screening beginning approximately 3 years after initiating vaginal intercourse, but no later than age 21 5
- Prostate cancer: Discussion about PSA testing for men starting at age 50 5
Recommendations for Healthcare Providers
Do not routinely recommend the Galleri test for cancer screening until clinical utility is established through completed clinical trials.
Continue to follow established screening guidelines from organizations like the American Cancer Society for specific cancers.
If patients inquire about the Galleri test:
- Explain that it is still investigational
- Discuss the ongoing clinical trials
- Emphasize the importance of continuing recommended conventional screening tests
- Clarify that the test is not currently included in any major screening guidelines
For patients interested in participating in research, provide information about ongoing clinical trials evaluating the Galleri test.
Conclusion
The Galleri test represents a promising approach to multi-cancer early detection, but its clinical utility has not yet been established. Until results from large randomized trials like NHS-Galleri are available and incorporated into official guidelines, healthcare providers should continue to follow established cancer screening recommendations.