Last Monday, the Food and Drug Administration (FDA) approved the use of an innovative blood test called Shield, developed by Guardant Health, for colon cancer screening. Although the test is not expected to replace colonoscopies, it has generated excitement among physicians, who see significant potential to increase detection rates for one of the deadliest cancers in the U.S. Shield, which was previously available to physicians as a screening tool at a cost of $895, could now be more affordable thanks to coverage likely to be offered by Medicare and private insurance companies following FDA approval. Arvind Dasari, M.D., associate professor in the department of gastrointestinal and medical oncology at the University of Texas MD Anderson Cancer Center, described the approval as a "welcome development," although he cautioned that "we will have to wait and see what the impact will be on improving detection and reducing mortality."
Data and Efficacy
The American Cancer Society estimates that more than 53,000 people will die of colorectal cancer this year. According to research published in March, Shield has demonstrated 83% effectiveness in detecting colorectal cancers, working by identifying DNA released by cancerous tumors into the bloodstream. However, its effectiveness varies according to the stage of the cancer, being more efficient in advanced stages, where more DNA is released. In contrast, it only detected 13% of polyps in early stages. The Shield test should be performed at least every three years, starting at age 45, the same age recommended to begin colorectal cancer screening. It is important to note that a positive test result does not constitute a definitive diagnosis. If the results indicate the possible presence of cancer, patients should undergo a colonoscopy to confirm the presence and stage of tumors. Robert Smith, senior vice president of Early Cancer Detection Science at the American Cancer Society, stressed that "a test like this is not complete if it is positive and a colonoscopy has not been performed."
Comparison with Other Screening Methods
Shield is the second blood test approved for colon cancer screening, following Epigenomics' Epi proColon, approved in 2016. However, Epi proColon has had limited use due to concerns about its accuracy and lack of coverage by Medicare and private insurance. Despite advances in screening, colon cancer rates have increased worryingly in people younger than 55 years, while declining in adults older than 60 years.
The Importance of Early Detection
Colorectal cancer is one of the few cancers that can be prevented by early detection, with colonoscopy being the most accurate method of detection. However, screening rates remain low, with less than 60% of eligible individuals having received their recommended screening. According to Dr. Sapna Syngal, director of strategic planning for cancer prevention and early detection at Dana-Farber Cancer Center, "the biggest problem with colon cancer right now is that a significant portion of the population is not getting screened." The approval of Shield represents a significant advance in the fight against colon cancer, offering a less invasive and potentially more accessible alternative for screening. However, it remains crucial that patients understand the importance of a follow-up colonoscopy in the event of a positive result. With the hope that this new test will increase detection rates, physicians and public health experts expect to see a positive impact on reducing colorectal cancer incidence and mortality in the coming years.
El Autor
