Colon cancer is one of the forms of cancer that is rarely talked about or reported early. Besides, while it initially affected older people — those over the age of 50, it is increasingly being observed in those in their 40s. As a result, its early detection becomes increasingly important. According to a study published in The New England Journal of Medicine in 2023, a cell-free DNA blood-based test can help detect colorectal cancers in the early stages. This blood test helped researchers detect colorectal cancer accurately in about 83% of the people with the condition, despite them not experiencing symptoms.
The results of clinical trials from this study showed that in an average-risk screening population, this cell-free DNA (cfDNA) blood-based test had 90% specificity for advanced neoplasia (invasive cancer) and 13% sensitivity for advanced precancerous lesions.
Colon cancer: Third most common cancer
According to World Health Organization, colon cancer is the third most common type of cancer seen across the globe, accounting for 10% of all cancer cases worldwide. This is also one of the most common types of cancer seen in men nowadays. It is more commonly seen in people at or above the age of 50. However, it is often diagnosed in advanced stages, when treatment options are limited. “Its early symptoms include a change in bowel habits, prolonged periods of constipation, blood in stools, unexplained weight loss and anemia. The prognosis of colon cancer varies depending on the stage when it is diagnosed,” shares Dr Hemanth G N, consultant, surgical oncology and robotic surgery, Manipal Hospitals, Bangalore. He also adds that higher survival rates are seen in the case of early detection of the condition.
Colon cancer and rectal cancer: What’s the difference?
While colon and rectal cancer are often confused as they have some similar symptoms, experts share that the conditions are quite distinct. As the names suggest, colon cancer occurs in the large intestine and rectal cancer affects the rectum. Moreover, treatment methods differ. “Colon cancer is usually treated surgically, followed by chemotherapy. However, rectal cancer treatment includes a combination of chemotherapy, radiotherapy and immunotherapy,” explains Dr Jagannath Dixit, senior consultant, surgical oncology, Aster CMI Hospital, Bangalore.
Dr Hemanth shares that while cases of rectal cancer are rising more steeply as compared to colon cancer in India, the reverse is true in the West. He adds, “Lifestyle habits like consumption of alcohol, excessive smoking and consumption of red meat could be contributing to this.”
What do experts say about cfDNA test for colorectal cancer detection?
The study focused on early detection of colorectal cancers. It included about 8,000 individuals between the ages of 45 and 84 at average risk of colorectal cancer — they were already undergoing routine checkups and screenings. Dr Hemanth shares, “During the early or precancerous stage of colon cancer, fragments of DNA are released in the blood, which can be detected by the blood test.”Â
Dr Dixit adds that currently, there are no tests for the early detection of colon cancer. He says, “The cfDNA blood test can detect colon cancer in case of early relapse or recurrence, which is not possible through a CT scan.” In the case of 65 of these people, colorectal cancer was later confirmed with a colonoscopy, a medical procedure where the expert examines the insides of the large intestine for any signs of abnormality.
Although the cfDNA test can accurately detect cancer in 83% of the people with colon cancer, it cannot detect precancerous lesions. Dr Dixit says, “At the same time, false-positive results were seen in 10% of the cases. The test was also unable to detect precancerous lesions, whereas colonoscopies help in the detection and removal of precancerous lesions at a treatable stage.” Experts share that while the blood test for early cancer detection is a game-changer, the false positives can be a cause for concern. “More research needs to be done on how frequently one should get the cfDNA test.
Colorectal cancer: Early detection is key
Health experts point out that though colorectal cancer is common and can be detected with early screening, only 50% of those with the condition go for tests. Dr Dixit says that the early detection of colorectal cancer is beneficial as it is at a treatable stage. “However, as the cancer progresses, treatment includes a mix of surgery and chemotherapy — it can then be difficult to treat,” he said.
Experts share that some people seek medical advice only after the cancer has spread and leads to extensive blood loss. “They visit the hospital when the tumor has become so enlarged that it causes intestinal blockages,” adds Dr Hemanth.
Takeaways
- Researchers recently found a blood test that can detect colorectal cancer at an early stage.
- While the cfDNA test could accurately detect cancer in 83% of the people with colorectal cancer, it could not detect the precancerous lesions.
- Early detection of colorectal cancer is beneficial as it is at a treatable stage.
