Increasing Cystatin C and Cathepsin B in Serum of Colorectal Cancer Patients.

Background: The aim of this study was to measure levels of cathepsin B (CatB) and cystatin C (CysC) and determine the CatB/CysC ratio in serum samples from patients with colorectal cancer (CRC), benign diseases of the digestive system, and other malignancies.
Methods: The serum specimens of 95 patients with CRC, 23 with benign diseases of the digestive system, 60 normal controls and 87 with other cancers were collected to measure the level of CysC and CatB. The CatB/CysC ratio was then calculated.
Results: There was a significant difference between the normal group and the CRC group (p < 0.01) in CysC serum levels. There were also differences in CatB levels and in the ratio of CatB/CysC between CRC patients and healthy controls or those with benign diseases of the digestive system (p < 0.01) and between those with carcinoma (highly-differentiated and poorly-differentiated) and those with adenoma (p < 0.01). The CysC, CatB, and CatB/ CysC levels were in the same range in other malignancies and CRC.
Conclusions: These results suggest that CysC could exclude normal samples, while the level of CatB and the CatB/ CysC ratio could distinguish CRC from benign diseases of the digestive system and thus has important value in early diagnosis of CRC.