For the study, researchers estimated the risk of developing and dying from colorectal cancers among 100,000 adults at average risk for these tumors. Scientists calculated the risks based on the recommended screening schedule for different kinds of tests: a colonoscopy every 10 years, a stool-based test every one to three years, or a blood test every three years.
After analyzing the data, the researchers estimated that about two and a half times as many people may die of colorectal cancer with blood tests as with colonoscopies, according to findings published in the Annals of Internal Medicine.
“Blood-based testing every three years may be much more convenient and palatable, but its expected benefit is substantially less profound,” says lead study author Uri Ladabaum, MD, a professor and director of the gastrointestinal cancer prevention program at Stanford University School of Medicine in California.
“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,” Dr. Ladabaum says.
Colonoscopy and Stool Tests Outperform Blood Tests for Colorectal Cancer Screening
Compared with not getting screened at all, people who get a colonoscopy every 10 years are 79 percent less likely to develop colorectal cancer and 81 percent less likely to die from these tumors, the study found.
Similarly, annual stool-based testing was associated with a 71 percent lower risk of developing colorectal cancer and a 75 percent lower risk of dying from these tumors than not getting screened at all.
The magnitude of risk reduction wasn’t as pronounced with blood tests, which were associated with a 42 percent lower risk of developing colorectal cancer and 54 to 56 percent lower risk of dying of these tumors than getting no screening at all.
Still, the results suggest that blood tests might be one way to reduce risk for people who otherwise wouldn’t get screened at all, says Electra Paskett, PhD, a professor of cancer research and director of the division of cancer prevention and control at The Ohio State University in Columbus.
“The best test is the test that gets done,” says Dr. Paskett, who wasn’t involved in the new study. Some people at low risk who have no personal or family history of colorectal cancer may be able to consider a blood test, Paskett says.
Some Blood Tests for Colorectal Screening Require Follow-Up Colonoscopy
Because blood tests are routinely done as part primary care visits, this may be an easy way to get more people screened for colorectal cancer, says Samir Gupta, MD, a professor and co-lead of the cancer control program at Moores Cancer Center at the University of California San Diego.
“But this is only part of the screening episode,” says Dr. Gupta, who wasn’t involved in the new study.
“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” Gupta says. “No noninvasive test can detect or prevent colorectal cancer without a colonoscopy follow up of abnormal tests.”
Read the full article here
