Positive Results for a Blood Test to Screen for Colon Cancer

A recent study has unveiled a promising blood test for colon cancer, providing a fresh approach to screening for one of the leading causes of cancer-related deaths. This test, aimed at detecting DNA fragments released by tumour cells and precancerous growths, has already entered the US market with a price tag of $895. However, it awaits FDA approval, and most insurance providers do not cover its cost. Guardant Health, the manufacturer of the test, remains optimistic about receiving FDA authorisation later this year.

In the study, the blood test demonstrated a success rate of 83% in identifying cancers. Still, it fell short in detecting most precancerous growths typically detected by colonoscopy, the gold standard for colon cancer screening. Colonoscopies detect tumours and play a crucial role in preventing the disease by removing precancerous growths known as polyps.

Despite colonoscopy’s effectiveness in identifying cancer and precancerous growths, many individuals are deterred from undergoing the procedure due to the inconvenience of taking time off work and the bowel preparation involved, which includes the consumption of a laxative. As a more convenient alternative, annual stool tests allow individuals to submit samples to a lab for analysis.

Colon cancer screening is recommended for healthy adults aged 45 to 75 at average risk, with the screening frequency depending on the chosen test. While routine colonoscopies are recommended every ten years, Guardant suggests testing with its blood test called Shield every three years. However, similar to stool tests, an abnormal result from the blood test necessitates a follow-up colonoscopy, potentially leading to additional out-of-pocket expenses.

The study, funded by Guardant and published in the New England Journal of Medicine, involved 7,861 participants who underwent both a colonoscopy and a blood test. While the blood test successfully detected 83% of the cancers identified by colonoscopy, it missed detection in 17% of cases, placing it on par with stool-based tests.

Notably, the study also uncovered several false positives, falsely indicating cancer in 10% of cases, which were not confirmed by subsequent colonoscopies. This underscores the necessity for further research to determine if the blood test may detect other cancers and produce misleading results.

Colorectal cancer ranks as the second leading cause of cancer deaths in the United States and the third worldwide. With over 153,000 new cases and 53,000 deaths expected this year in the US alone, enhanced screening efforts have the potential to reduce mortality rates associated with the disease.

Dr. Nabil Mansour of Baylor College of Medicine expressed optimism about having a reliable blood test option for colon cancer screening. While he will continue to recommend colonoscopies for his patients, having an alternative screening method offers greater flexibility and accessibility in detecting and preventing colon cancer.

In conclusion, the development of innovative screening methods, such as the blood test for colon cancer, signifies a significant stride in combating this deadly disease. By offering a range of screening options, healthcare providers can empower individuals to take proactive measures toward protecting their health and well-being.

Written by Mr. Shazlee Ashan

BSc Pharmacy, MSc Endocrinology, PgDip Infectious Diseases, Ipresc