A new way to screen for colon cancer may be on the horizon, study suggests

The potential approval of the first blood test for colorectal cancer this year could mark a significant breakthrough in cancer detection, potentially increasing the number of diagnoses for the second-highest cause of cancer death in the United States. While experts emphasize that the test would not replace colonoscopies, it could offer a less invasive alternative and encourage more people to undergo colorectal screenings.

Dr. William Grady of Fred Hutchinson Cancer Center in Seattle led the research on the blood test, known as Shield, developed by Guardant Health based in California. The study, published in the New England Journal of Medicine, found that the test was 83% effective in detecting colorectal cancers, a promising result according to outside experts.

Colonoscopy remains the most accurate method for detecting colon and rectal cancers, as well as precancerous lesions. However, barriers such as the preparation required before the procedure and the need for anesthesia contribute to low screening rates, with less than 60% of eligible individuals being up to date.

Guardant's blood test detects DNA released by cancerous tumors and is particularly effective in detecting later-stage cancers. However, its efficacy in detecting early-stage polyps, when treatment is most effective, is lower, as precancerous polyps do not release tumor DNA.

While the blood test could offer a less burdensome screening option, it would still require follow-up with a colonoscopy for a definitive diagnosis and treatment plan. The Food and Drug Administration is expected to review the Shield test for approval later this year. If approved, it would be recommended every three years starting at age 45, with colonoscopy still necessary for individuals with symptoms or a family history of colorectal cancer.