Is serum matrix metalloproteinase 9 a useful biomarker in detection of colorectal cancer? Considering pre-analytical interference that may influence diagnostic accuracy

I read with great interest the article by Hurst et al (2007) , which was recently published in the Br J Cancer . The authors described elevated serum concentration of matrix metalloproteinase 9 (MMP-9) in patients with colorectal neoplasia compared with the MMP-9 concentration in symptomatic patients without non-neoplastic conditions. On the basis of this result of increased serum MMP-9 concentration the authors developed a logistic regression model including age, sex, smoking history, abdominal pain, and weight loss as additional factors for the prediction of malignant colorectal disease. The authors concluded that increased serum MMP-9 concentrations could be useful to stratify patients into those with low- and high-risk of malignancy to spare patients unnecessary colonoscopy. Some of the authors of this article already elaborated detailed study protocols including sample size calculation, potential selection bias, confounders, methods of analyses study protocols to evaluate the potential of serum MMP-9 as a screening test for colorectal cancer ( Ryan et al, 2006 ; Wilson et al, 2006 ). Apparently based on the pilot data described in the mentioned report of Hurst et al (2007) and the prevalence data of colon cancer, it was calculated that 23 100 people from 29 practices have to be recruited to identify the 700 participants needed for this study ( Wilson et al, 2006 ).