Blood test to detect colon and rectal cancer

Researchers from Hospital Del Mar in Barcelona have confirmed the usefulness of a blood test for detecting colon and rectal cancer. This discovery aims to increase public participation in screening programs, which are currently carried out through stool testing.

The blood test can provide diagnostic performance comparable to that of current methods for detecting colon tumors, concludes a paper published in Annals of Oncology. The researchers used a liquid biopsy technique to detect mutations and DNA modifications associated with tumors.

“Screening programs reduce cancer-related problems and mortality, but one of their problems is low public participation. Finding a biomarker that can be identified through routine testing could contribute to this,” explains Xavier Bessa, head of the digestive system service at Hospital del Mar.

The test looks for tumor genetic material in the blood (liquid biopsy), which is more often present in later stages.

The population-based colon cancer screening program in Catalonia targets men and women aged 50 to 69 years and consists of an immunological test every two years to detect occult blood in the stool, which cannot be seen with the naked eye. You need to make a request, go to the pharmacy to pick up a container, donate the feces and return it to the pharmacy. This is not a very complicated procedure, but only 50% of the susceptible population is involved, and this fact affects the ability to detect tumors, especially at an early stage.

“Exploring our strategies to improve participation and the effectiveness of the tests we use is a priority for population-based prevention programs, and this study is a very important step in that regard,” said Sarah Buron, head of the Epidemiology and Marine Assessment Service.

In this sense, the study analyzed 623 blood samples, 318 of which corresponded to people who had a hospital colonoscopy between 2017 and 2018 after testing positive in a colon cancer screening program.

The test, which looks for tumor DNA in the colon by analyzing various changes, has a sensitivity of more than 90% in tumors and 23% in precancerous polypoid lesions before tumors appear. It’s a proof of concept, a first step that can be taken, but “the liquid biopsy technique has been shown to be effective in detecting tumors before they show symptoms,” says researcher Joana Vidal, an oncology assistant.

Although detection of tumor genetic material in the blood (liquid biopsy) is estimated to provide sensitivity similar to that of conventional tests, there is still a way forward, which Dr. Vidal believes is to predict the diagnosis: “At a very early stage, the release of genetic material from the tumor into blood is much lower and we need an advanced and innovative technique because we want to diagnose very early tumors, from stages 1 to 3; 4 is already a metastatic tumor. We also try to look for precancerous lesions when we know the polyp will eventually develop into a tumor.”

Colorectal cancer is the most common cancer in people over 50 years of age.

Using the same technology as the Hospital del Mar researchers, a parallel study was conducted in the United States involving more than 20,000 people, which Dr. Bessa said should demonstrate greater population adherence to screening programs through analysis. blood.

Early detection is a major factor in survival for colorectal cancer, which is most common among people over 50 and accounts for 15% of detected malignancies in Spain. It develops inside the colon from small lesions that can be removed before a tumor develops.

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Anthony Lopez Tovar