A new marker for colorectal cancer

RM. McLoughlin, E. Shiel, SS. Sebastian, B. Ryan, HJ O’Connor, C.O. Morain
Department of Gastroenterology, Adelaide & Meath Hospital, Tallaght, Dublin 24, Ireland
INTRODUCTION: Although all agree on the need for colorectal cancer screening, the ideal screening method remains controversial. A screening tool which is noninvasive, with a high sensitivity and specificity, and cost-effective in comparison with current screening methods is desirable.
Pyruvate kinase is a key enzyme in the glycolytic pathway and determines the relative amount of glucose that is channelled into synthetic processes or used for glycolytic ATP production. Pyruvate kinase exists in different isoenzymes depending on metabolic requirements. Tumour M2-PK exists in cancer cells where a high capacity for nucleic acid synthesis is required.
AIM: To evaluate tumour M2-PK as a screening tool for colorectal cancer.
Stool was collected from subjects pre-colonoscopy and stored at -8°C. Tumour M2-PK was analysed using an ELISA technique.
Our study included 120 patients: 65 patients with normal colonoscopy, 30 patients with adenomas, and 25 patients with colorectal cancer.
The tumour M2-PK values were as follows in the table:
     Normal     Adenoma    Cancer

Min         0.17          1.9            3.2
Max        6.6            33             52
SD         1.1             6.6            16
Using a cut-off of 4 U/ml the sensitivity of tumour M2-PK for colorectal cancer was 92% with a specificity of 95%. For adenomas the sensitivity of tumour M2-PK was 63% with a specificity of 92%.
Tumour M2-PK, a simple ELISA test, has a high sensitivity and specificity for colorectal cancer and an acceptable sensitivity and high specificity for adenomas, in comparison with current accepted screening methods. Its noninvasive nature makes it an ideal screening tool for average risk individuals, to identify those who need more invasive screening.
Abstract presented at the Digestive Disease Week (DDW) 2005, May 14-19, 2005, Chicago/USA