Evaluating faecal tumour M2 pyruvate kinase as a screening test for colorectal carcinoma.

Abstract

Colorectal carcinoma (CRC) is the third most common malignancy worldwide. Screening for CRC is linked with a decreased incidence of the disease and also a lowered mortality rate. Most screening programs have relied on Guaiac-based Faecal Occult Blood Test (G-FOBT); however this test has the main limitation of being poorly sensitive to CRC since it fails to detect non-bleeding colorectal adenomas and CRC. Tumour M2 Pyruvate Kinase (Tumour M2-PK) is the dimeric form of pyruvate kinase and is characteristically found in proliferating cells, especially tumour cells. In CRC and to a lesser extent in colorectal adenomas, Tumour M2-PK is released into the stools and may be quantified using an Enzyme-linked immunosorbent assay (ELISA). The aim of this study was to compare Faecal Tumour M2-PK assay and GFOBT head-to-head using colonoscopy as the gold standard. Faecal Tumour M2-PK assay and G-FOBT were evaluated in 30 patients undergoing colonoscopy of which 22 patients were normal or had hyperplastic/inflammatory polyps only, 5 patients had low-grade dysplasia colorectal adenomas while 3 patients had other gastro-intestinal tract (GIT) inflammatory conditions. Specificity and sensitivity of G-FOBT for colorectal adenomas were 100% and 0% respectively while specificity and sensitivity of faecal Tumour M2-PK for colorectal adenomas were 84 - 95.5% (depending if results of patients with GIT inflammatory conditions are included) and 20% respectively. This study showed that both tests have no potential in discriminating between normal individuals and patients bearing adenomas; therefore these tests may have very limited role in decreasing CRC incidence rate and should not be recommended as screening tests for CRC.