Colorectal cancer (CRC) is one the leading causes of cancer death worldwide. However, advances in cancer care are needed to optimise limited resources. Recently, novel strategies to identify accessible and inexpensive biomarkers to guide management have yielded several novel inflammatory prognostic biomarkers. This thesis expands on these ideas by re-evaluating routinely collected clinical data for utility as prognostic biomarkers in cancer. These ideas are anchored on the focal idea that inflammation plays a key role in cancer. Chapter one of this thesis reviews CRC, the role of inflammation in cancer and prognostic biomarkers. Chapter two investigates the lymphocyte-to-monocyte ratio (LMR) as a potential novel prognostic marker of CRC. This published work provides a definitive outline for LMR in each stage of CRC, identifying it as an independent prognostic marker that provides added value over other established biomarkers. Chapter three expands this work, investigating the utility of serially re-measuring inflammatory markers throughout treatment. This paper explores the prognostic implications of changes in systemic inflammation peri-operatively. Chapter four highlights the potential of repurposing data by investigating serum bicarbonate as a biomarker linked to inflammation. This paper establishes serum bicarbonate to be independently associated with peri-operative mortality but not long-term overall survival and provides preliminary evidence against serum bicarbonate supplementation as a cancer treatment. Chapter five re-examines tumour sidedness as a prognostic tool. Recent evidence has suggested sidedness to be not only prognostic but predictive of treatment efficacy. This work cautions against repurposing data too quickly, identifying sidedness as a surrogate for inflammatory and genomic markers. Chapter six summarizes the thesis, highlighting the potential of repurposing data for biomarker discovery and suggesting avenues for future study.