Recent research has revealed that while blood tests for colorectal cancer screening may offer greater convenience, they significantly lag behind colonoscopies and stool-based tests in terms of preventing deaths. A study published in Annals of Internal Medicine suggests that blood tests, though less invasive, may not be as effective in saving lives compared to other screening methods.
Blood tests: a less invasive but also less effective alternative
A breakthrough in non-invasive colorectal cancer screening, blood tests are gaining attention for their convenience and comfort compared to colonoscopies, which many individuals find unpleasant. However, a study led by Dr. Uri Ladabaum, a professor at Stanford University School of Medicine, casts doubt on the effectiveness of blood tests in reducing cancer-related mortality.
According to the study, “Blood-based testing every three years may be much more convenient and palatable, but its expected benefit is substantially less profound.” The researchers estimate that blood tests could lead to more than twice the number of deaths from colorectal cancer compared to colonoscopies. While blood tests are an attractive option for many people, they are not as reliable in preventing the disease when compared to more established methods.
Colonoscopy and stool tests still the Gold Standard
The study’s findings are clear: colonoscopies and stool-based tests far outperform blood tests in reducing the risk of colorectal cancer and preventing related deaths. A colonoscopy every 10 years lowers the risk of developing colorectal cancer by 79% and the risk of dying from the disease by 81%. Similarly, annual stool-based testing offers a 71% reduction in the risk of developing colorectal cancer and a 75% reduction in mortality.
The benefits of blood tests were less pronounced, with a 42% lower risk of developing cancer and a 54-56% reduction in the risk of death from the disease. While this is a notable improvement over not screening at all, it is still far behind the protection offered by colonoscopies and stool tests.
Blood tests: a potential option for the reluctant
Despite their limitations, blood tests for colorectal cancer screening can still serve a purpose, especially for those who would otherwise avoid screening altogether. Dr. Electra Paskett, a cancer researcher at The Ohio State University, pointed out that the primary goal is to get more individuals screened, regardless of the method. She emphasized that “The best test is the test that gets done.” Blood tests may appeal to people who are at low risk and lack a personal or family history of colorectal cancer. For these individuals, blood tests could be a viable first step toward early detection.
However, it is important to note that blood tests cannot fully replace colonoscopies. As Dr. Samir Gupta, a professor at the University of California San Diego, explained, “No noninvasive test can detect or prevent colorectal cancer without a colonoscopy follow-up of abnormal tests.” Blood tests alone cannot provide the comprehensive screening needed for accurate diagnosis. In cases where the blood test returns an abnormal result, a follow-up colonoscopy is essential to confirm the diagnosis and allow for proper intervention.
The role of follow-up colonoscopies
One of the challenges with blood tests is that many individuals may not follow up with a colonoscopy if the results are abnormal. This potential gap in screening could undermine the effectiveness of blood tests in the long run. Dr. Gupta raised concerns that if people with abnormal blood test results do not proceed with a colonoscopy, the overall impact on reducing colorectal cancer rates will be minimal. “If rates of blood test uptake are high, but low proportions of people with abnormal tests go to colonoscopy, we effectively have not increased the pool of people who have received guideline-appropriate screening.”
To make blood tests truly effective, it is crucial to ensure that those with abnormal results are referred for colonoscopy. Without this critical follow-up, the benefits of blood tests are significantly diminished.
The bottom line: colonoscopies are still the best bet
While blood tests for colorectal cancer screening may offer a less invasive alternative, they do not offer the same level of protection against the disease as colonoscopies or stool tests. The study underscores the importance of continuing to prioritize these more established methods in order to reduce the risk of colorectal cancer and prevent deaths.
For now, “If you are willing and able to do stool-based testing or screening colonoscopy, at present, that will optimize your chances of protection against getting colorectal cancer or dying from it,” said Dr. Ladabaum. Though blood tests can be a useful screening tool for those who might otherwise forgo screening, colonoscopies remain the gold standard for early detection and prevention of colorectal cancer. As research and technology evolve, it remains to be seen whether blood tests will play a more prominent role in the future of colorectal cancer screening.
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