Vitamin C for Colorectal Cancer: A clinical window study to assess high dose vitamin C administration in colorectal cancer patients

Interventions: Participants will receive a high dose vitamin C infusion (1g vitamin C/kg body weight) each day for four days prior to surgical resection of tumour. All infusions will be administered by research nurse.
Primary outcome(s): Ascorbate uptake - plasma, normal colon tissue, tumour tissue (measured by HPLC with electrochemical detection) - composite primary outcome[Treatment group: at diagnostic colonoscopy (blood and tissue), prior to each of four daily vitamin C infusions (blood), following surgical resection of tumour (tissue)
Control group: at diagnostic colonoscopy (blood and tissue), prior to surgery (blood), following surgical resection of tumour (tissue)
];Changes in tumour biology - HIF-1 protein levels/activity i.e. downstream gene expression e.g. VEGF, GLUT-1, BNIP3, CAIX (measured by Western blotting and ELISA)[Tissue taken at diagnostic colonoscopy and tumour resection];Changes in tumour histopathology e.g. vitamin C transporter status, immune infiltrate, micro-vessel density (measured by immunohistochemistry)[Tissue taken at diagnostic colonoscopy and tumour resection]
Study Design: Purpose: Treatment; Allocation: Randomised controlled trial