Cancer-related pain is a distressing symptom that can have a significant impact on patients’ lives. About two-thirds of patients with advanced cancer experience pain, but despite this high prevalence cancer-related pain can often be undertreated. The goal of C-PAIN is to determine whether delivering up-front pharmacogenomic (PGx) results to oncology providers and patients will help inform opioid medication selection and dosing in order to improve the efficacy of common therapies for cancer-related pain.