Evaluating a Pharmacogenetic Testing Panel in Patients Suspected to be at Increased Risk for Pharmacogenetics-related AEs While Receiving Fluoropyrimidine or Irinotecan Therapy

Inclusion Criteria: * Age \> 18 years * Prospectively enrolled cases: A. Suspected to carry an actionable DPYD phenotype per MGI and initiating treatment with systemic FP OR suspected to carry an actionable UGT1A1 phenotype per MGI and initiating treatment with irinotecan for cancer B. The ability to understand and the willingness to sign a written informed consent. * Retrospective cases: A. Confirmed actionable DPYD phenotype before treatment with systemic FP OR confirmed actionable UGT1A1 phenotype before treatment with irinotecan B. Clinician initiated dose reduction of the fluoropyrimidine or irinotecan therapy based upon genotype result * Retrospective controls: A. Suspected actionable DPYD phenotype per MGI and treatment with systemic FP OR suspected actionable UGT1A1 phenotype per MGI and treatment with irinotecan Exclusion Criteria: * For prospective cases, prior treatment with systemic FP if suspected to carry an actionable DPYD phenotype * For prospective cases, prior treatment with irinotecan if suspected to carry an actionable UGT1A1 phenotype * For prospective cases, inability to understand consent or make health-related decisions * History of allogeneic bone marrow transplant prior to genotype testing * History of liver transplant