What is the new FDA-approved blood test for colon cancer screening?

FDA-Approved Blood Test for Colorectal Cancer Screening

The only FDA-approved blood test for colorectal cancer screening is the Epi proColon test, which detects methylated Septin 9 (SEPT9) DNA in plasma. 1 This test was approved by the FDA in April 2016 as a screening option for average-risk adults aged 50 years and older who decline recommended screening methods like colonoscopy, stool-based tests, or CT colonography. 1

Test Characteristics and Performance

The Epi proColon test works by detecting methylated SEPT9 DNA in plasma samples using a real-time PCR assay. Key performance characteristics include:

• Sensitivity: Studies show varying sensitivity rates:

  • 48% sensitivity in the FDA approval study 1
  • 68% sensitivity for all CRC stages in a prospective clinical trial 2
  • 64% sensitivity for stage I-III CRC 2
  • Up to 90.8% sensitivity in some studies 3

• Specificity: Approximately 80-88% 2, 4

• Limitations:

  • Low sensitivity for detecting advanced adenomas (11.2%) 1
  • Lower specificity compared to FIT (81.5% vs 97.4%) 4
  • Cannot effectively detect precancerous polyps 1

Position in Screening Guidelines

The Epi proColon test is generally positioned as a secondary screening option:

• The NCCN guidelines note that it "may provide an option for screening for those who refuse other screening modalities, but its ability to detect CRC and advanced adenoma is inferior to other recommended screening modalities." 1

• The US Preventive Services Task Force and US Multi-Society Task Force do not recommend the Septin9 test as a primary screening method due to its inferior performance characteristics compared to other screening tests. 1

• The Asian Pacific Association of Gastroenterology guidelines state that it is "indicated for screening participants who have been offered but declined first line CRC screening tests, such as FIT, and diagnostic colonoscopy is still necessary after a positive Epi proColon result." 1

Clinical Application

When considering the Epi proColon test:

• Target population: Average-risk adults aged ≥50 years who refuse recommended first-line screening methods 1, 5

• Testing procedure: Simple blood draw requiring no bowel preparation or dietary restrictions

• Follow-up: Positive results require diagnostic colonoscopy for confirmation 1

• Screening interval: Annual testing is suggested by microsimulation modeling, similar to FIT 5

Advantages and Disadvantages

Advantages:

• Minimally invasive (simple blood draw)
• No bowel preparation required
• May increase screening compliance in patients who refuse other methods 5
• High negative predictive value (99.8%) 4

Disadvantages:

• Lower sensitivity for cancer detection compared to colonoscopy
• Poor sensitivity for precancerous lesions
• Lower specificity than FIT, leading to more false positives 4
• Relatively expensive compared to FIT 1

Emerging Research

Recent research suggests the Epi proColon test may have value in detecting early-onset colorectal cancer (EOCRC) in individuals under age 50, with one study showing 88.9% detection rate in EOCRC cases compared to 4.2% in healthy controls under 50 years old 3. This could potentially address an emerging public health concern, though more research is needed before clinical implementation for this indication.

In conclusion, while the Epi proColon blood test offers a convenient alternative for patients who decline recommended screening methods, its performance limitations mean it should not replace first-line screening options like colonoscopy or FIT for most patients.