An ideal method for colorectal cancer screening?
Colorectal cancer (CRC) is the third most frequent malignant neoplasm globally. In Europe CRC is the second most common cause of cancer death in women (breast cancer is the most common), and the third most common in men (after prostate and lung cancer). Data are similar from other Western countries. However if the condition is diagnosed very early via effective screening programmes, mortality can be greatly reduced, and various screening options are available.
The US guidelines advise screening people every ten years from the age of 50 via colonoscopy, or every five years via virtual colonoscopy, flexible sigmoidoscopy or double-contrast barium enema. The reported mortality reduction ranges from 60–70% in the participating population but, because of the nature of the procedures, screening adherence is problematical. The EU recommends biennial screening using the fecal occult blood test (FOBT). Such tests are usually mailed to older European residents to carry out at home, with both instructions on use and where to return tests on completion. Although this population screening method is easy and convenient it is not very reliable; specificity is low. Ingesting certain foods and drugs prior to testing, as well as conditions such as haemorrhoids, gastrointestinal ulcers and inflammations can all give false positive results. Sensitivity is also very low: various trials indicate that around 50% of tumours are not detected, and that reduction in mortality as a result of these screening programmes ranges from only 15–21%.
Although population screening utilizing CRC tumour markers would seem to be an ideal approach, in practice previously developed tests incorporating CEA combined with CA 19-9 have not provided high enough sensitivity. However, a project carried out by several Russian centres may well have found the solution. The researchers have developed a 3D hydrogel-based biochip that utilizes autoantibodies to detect specific, tumour-associated glycans in serum. This test format, which allows a more equal distribution of the molecular probes than planar systems, simultaneously measures protein-based tumour markers, the autoantibodies-to-glycans ratio, and immunoglobulin levels. By testing healthy controls, patients with CRC and patients with inflammatory bowel disease, it was possible to define both prognostic and diagnostic signatures. The prototype allowed diagnosis of CRC with a specificity of 95% and a sensitivity of 87%. The testing system is predicted to reach clinical laboratories in Russia in the near future. Hopefully the end result will be a simple, highly specific and sensitive test for CRC that can be performed at home.
