Aim: to evaluate the performance of fecal tumor M2 pyruvate kinase (M2PK) as a diagnostic biomarker for colorectal cancer (CRC) screening in high-risk or symptomatic populations.
Methods: consecutive patients (N=328) who were referred for elective colonoscopy were prospectively enrolled. One walnut-sized stool sample was collected from each patient for analysis of tumor M2PK content using an ELISA kit. No dietary restrictions were applied. The clinical pathologists who conducted the M2PK analyses were blinded to the patients' confirmed diagnoses. Levels of fecal tumor M2PK were compared with histopathological results from colorectal biopsies.
Results: of the 328 patients who underwent colonoscopy examinations, 197 (60.1%) were men and 131 (39.9%) were women. Based on histopathological examination, 83 (25.3%) patients had normal bowel histology, 42 (12.8%) patients had CRC, 67 (20.4%) patients had adenoma, 19 (5.8%) patients had inflammatory bowel disease, three (0.9%) patients had amoebic colitis, and 114 (34.8%) patients had infective colitis. The cutoff level for tumor M2PK concentration was defined as 4.00 U/mL. The sensitivity, specificity, positive predictive value, and negative predictive value of the M2PK test were 71.4%, 71.0%, 73.5%, and 94.4%, respectively. There was a significant association between CRC and fecal tumor M2PK level (P<0.001). The M2PK test detected 16 tumors among 67 (23.9%) cases of adenoma, eight tumors among 19 (42.1%) cases of inflammatory bowel disease, 35 tumors among 114 (30.7%) cases of infective colitis, and two tumors among three (66.7%) cases of amoebic colitis.
Conclusion: the fecal tumor M2PK test has good sensitivity and specificity for CRC detection, especially in high-risk or symptomatic populations.