Protein prognostic biomarkers in stage II colorectal cancer: implications for post-operative management

Colorectal cancer (CRC) poses a significant threat to many human lives worldwide and survival following resection is predominantly stage dependent. For early-stage cancer, patients are not routinely advised to undergo additional post-operative adjuvant chemotherapy. Acceptable clinical management guidelines are well established for patients in pTNM stages I, III and IV. However, recommendations for managing CRC stage II patients remain controversial and many studies have been conducted to segregate stage II patients into low- and high-risk of recurrence using genomic, transcriptomic and proteomic molecular markers. As proteins provide valuable insights into cellular functions and disease state and have a relatively easy translation to the clinic, this review aims to discuss potential prognostic protein biomarkers proposed for predicting tumour relapse in early-stage II CRC. It is suggested that a panel of markers may be more effective than a single marker and further evaluation is required to translate these into clinical practice.