Researchers from the Hospital del Mar, in Barcelona, have confirmed the usefulness of a blood test for the detection of colon and rectal cancer. The finding aims to increase the participation of the population in screening programs, which are currently carried out through stool analysis.
Through a blood test, a diagnostic performance comparable to that of current options for detecting colon tumors can be obtained, concludes the work, published in Annals of Oncology. Researchers have used the liquid biopsy technique to detect mutations and DNA modifications linked to tumors.
“Screening programs reduce the problems and mortality associated with cancer, but one of their problems is the low participation of the population. The search for a biomarker that can be identified with a routine analysis could favor it,” explains Xavier Bessa, head of the Digestive System service at the Hospital del Mar.
The population screening program for colon cancer in Catalonia is aimed at men and women aged 50 to 69 and consists of carrying out, every two years, an immunological test to detect hidden blood in feces that cannot be seen with the naked eye. You have to make the request, go to the pharmacy to pick up a container, deposit the feces and return it to the pharmacy. It is not a very complicated procedure, but only 50% of the susceptible population participates, a fact that has an impact on the ability to detect tumors, especially in the initial stage.
“Exploring our strategies to improve participation and efficiency of the tests used is a priority for population preventive programs and this study is a very relevant step in this regard,” according to Sara Burón, head of the Epidemiology and Marine Assessment service.
In this sense, the study has analyzed 623 blood samples, 318 of which correspond to people who underwent a colonoscopy at the hospital between 2017 and 2018 after testing positive in the colon cancer screening program.
The test, which searches for DNA from the tumor in the colon by analyzing different alterations, has a sensitivity of over 90% in tumors and 23% in preneoplastic polypoid lesions, prior to the appearance of the tumor. It is a proof of concept, the first step that can be taken, but “it has been shown that the liquid biopsy technique is effective in detecting the tumor before it gives symptoms,” says researcher Joana Vidal, assistant to the Oncology service.
Although the detection of genetic material from the tumor in the blood (liquid biopsy) is estimated to provide a sensitivity similar to that of the usual tests, there is still a way to go. And it consists, according to Dr. Vidal, of anticipating the diagnosis: “In very In the initial stage, the release of genetic material from the tumor into the blood is much lower, and we need an advanced and pioneering technique because we want to diagnose very early tumors, from stage 1 to 3; 4 is already a metastatic tumor. We also try to find preneoplastic lesions, when we know that the polyp will end up being a tumor.”
Using the same technology as the researchers at the Hospital del Mar, a study has been completed in parallel in the United States with more than 20,000 people that should demonstrate, according to Dr. Bessa, greater adherence of the population to screening programs through analysis. of blood.
Early detection is the main survival factor in colorectal cancer, the most common among people over 50 years of age and in Spain it represents 15% of malignant tumors detected. It develops inside the large intestine from small lesions, which can be removed before a tumor develops.
