Increased Plasma Superoxide Radical in Patients with Non-Metastatic Colorectal Cancer

Several studies have investigated the potential role of oxidative stress in the evolution of colorectal cancer. In most of these studies, oxidative stress was assessed indirectly by measurements of indices like lipid peroxidation, protein oxidation or antioxidant status. The present study was undertaken to directly assess systemic oxidative stress by measuring plasma superoxide radical (O₂^-·) in patients with non-metastatic colorectal cancer.

Twelve patients (6 males and 6 females) with a recent diagnosis of colorectal cancer and no signs of metastases and 12 healthy volunteers matched for age and gender were enrolled in the study. O₂^-· levels in plasma were assessed by application of a new ultra-sensitive fluorescent assay. Also lipid peroxidation levels in plasma were measured as thiobarbituric acid reactive species (TBARS).

In the plasma fraction of whole blood, there was a significant increase (47%) of O₂^-· levels in colorectal carcinoma patients as compared to healthy volunteers (P < 0.001). In fractionated plasma, no O₂^-· was detected in both groups. Plasma TBARS levels were increased by 81% in colorectal carcinoma patients as compared to controls (P < 0.001).

These data show that colorectal cancer, even at early (non-metastatic) stages, induces systemic oxidative stress as evidenced by increased O₂·^- levels measured in plasma. Given the important role of oxidative stress in carcinogenesis and the fact that O₂·^- is considered its primary parameter, our findings if confirmed in larger studies might establish the potential validity of O₂·^- as a new biomarker for colorectal cancer.