Pyruvate kinase M2 (tumor M2-PK) as a screening tool for colorectal cancer (CRC). A review

Introduction: Colonoscopy is currently supposed to be the best screening tool for colorectal cancer. However, the acceptance of the population is very poor although it has been included in screening programs in the German health system since 2002. Therefore, evaluation of additional screening tools seems to be of great interest. Recently testing for fecal occult blood (FOBT), genetic alterations or alterations in tumor metabolism (e. g., tumor M2-PK) are under investigation. Methods: The use of M2-PK measurement in the feces has been reported in 6 studies until today. The data of these studies were analyzed and critically reviewed. Results: The overall sensitivity of M2-PK is 77.9% concerning CRC. Specificity ranges from 74.3-83.3%. Overall sensitivity for adenomas is 45.9 %, increasing to 61.1 % for adenomas > 1 cm. A high percentage of positive results (90.4%) was also observed in patients with chronic inflammatory bowel disease. Conclusions: Compared to FOBT or genetic testing the M2-PK test seems to be superior for CRC screening. Concerning handling, effectiveness and analysis, M2-PK seems to be a good possibility for large scale-screening of colorectal carcinoma. It might even be used to detect larger adenomas. Elevated levels of M2-PK in patients with acute and/or chronic inflammatory bowel diseases are probably due to proliferation of epithelial cells and leucocytes in the inflammatory area.