Colon cancer: Blood test holds promise for detection – 03/16/2024 – Balance and Health

Early detection of colon cancer can prevent most deaths from the disease — about 73% of them — but only about 50% to 75% of middle-aged and older adults are being tested. According to doctors, one of the reasons for this is discouragement regarding monitoring methods.

There are two testing options for people at average risk of developing the disease. One of them is to have a colonoscopy every ten years or a stool test every one to three years, which varies depending on the test.

According to Dr. Folasade P. May, a gastroenterologist at the University of California Health Center in Los Angeles, “either you take this horrible laxative and a doctor puts an instrument up your butt, or you have to handle your own poop.”

But something much simpler is looming on the horizon: a blood test. Gastroenterologists say these tests could become part of the routine tests doctors order at an annual check-up.

“I think this is going to take off,” says John Carethers, a gastroenterologist and vice dean for health sciences at the University of California, San Diego.

About 53,000 Americans are expected to die from colon cancer this year. It is the second most common cause of cancer-related deaths in the United States. While the death rate among older adults has fallen, there has been an increase among the population under 55.

Current health guidelines recommend testing starting at age 45, but the problem is convincing more people to get tested.

This is where the blood test comes in. The test gained an advantage after the discovery that colon cancers and large polyps — clusters of cells that can become cancers — leave fragments of DNA in the blood.

A study carried out by the company Guardant Health and published last Wednesday (13) in The New England Journal of Medicine showed that the search for this type of DNA, called Shield, in an exam revealed 87% of cancers at an early and curable stage. . The false positive rate was 10%.

“This is going to be big news,” said May, who consults for Exact Sciences, maker of the Cologuard stool test.

But there is a caveat. Although it detects cancer, the blood test does not detect the majority of large polyps, finding only 13% of them. The fecal test can register 43%, and the colonoscopy, 94%, according to Carethers.

Although they are harmless, some polyps can become cancer. Therefore, doctors want to find and remove them all to avoid the disease.

For doctor Barbara Jung, director of the department of medicine at the University of Washington and president of the American Gastroenterology Association, patients should be fully informed before choosing to take a blood test.

Furthermore, they need to understand that, although the test can detect cancer in the early stages, it cannot prevent it because it is not good at finding polyps.

“We need to have this discussion” with patients, Jung said. She says, however, that the issue will fall to primary care doctors “who are already very pressed for time to go through a litany of tests and counseling.”

Doctors will also need to explain to patients that if the test result is unusual, they will need to schedule a colonoscopy to look for polyps or early-stage cancer and, if detected, remove them.

There is also no consensus on the frequency of this blood test. Guardant suggested a three-year interval, but the recommendation, according to Jung, is not established.

She added that she would love to know how the test performs in people too young for imaging tests, but that will require more study.

Jung is concerned about the increasing incidence of colon cancer among young people, and says it would be more attractive for people in their 30s to have a blood test to detect the disease. “That would be my biggest excitement.”

The big mystery, however, is the cost. Guardant filed a request with the FDA (drug and food regulatory agency in the USA) to define the price and sale of the blood test.

Currently, it is sold as a laboratory test, which does not require agency regulation, but is also not covered by health plans — costing US$895 (about R$4,472).

But the company says it will work with the government’s Medicare and Medicaid programs and private insurers to “finalize pricing” if the test is approved, according to Guardant spokesman Matt Burns.

According to William Grady, medical director of the gastrointestinal cancer prevention center at Fred Hutchinson Cancer Center and author of the Guardant-sponsored study, the company could agree to a price that makes the blood test comparable to the cost of imaging.

The Cologuard fecal test costs US$581 to US$681 (R$2,903 and R$3,403, in approximate values).

Colonoscopies, generally required at half the frequency of stool tests, cost US$1,250 to US$4,800 (R$6,246 and R$23,983), although some hospitals charge more. The average cost in the United States, generally covered by health plans, is US$2,750 (R$13,740).