Cancer Treatment Related Cardiovascular Toxicity: Comprehensive Myocardial and Vascular Phenotyping

Inclusion Criteria: * Age \>18 years * Gastrointestinal malignancy * Receiving fluoropyrimidine chemotherapy Exclusion Criteria: * Participants unable or unwilling to provide consent * Participants that have a conventional contraindication for magnetic resonance imaging (MRI) including permanent implantable cardiac devices, ferromagnetic implants, pregnancy, large body size not fitting into the scanner bore and severe claustrophobia will be excluded * Participants that have a conventional contraindication for adenosine stress perfusion including a history of trifascicular block or of second-degree heart block or higher on ECG, or uncontrolled asthma. * Participants with significant renal impairment (eGFR\<30ml/min) * History of allergy to adenosine, gadolinium or iodinated contrast * Patients with terminal illness (life expectancy \<6 months) will be excluded.