Precision Medicine Guided Treatment for Cancer Pain

Pain is one of the most burdensome symptoms associated with cancer and its treatment, and opioids are the cornerstone of clinical pain management in cancer patients. Yet, individual patient responses to opioids vary widely, and the patient's genotype contributes to this variability. Specifically, cytochrome P450 2D6 (CYP2D6) genotype has important relevance for response to opioid analgesics that depend on CYP2D6 for bioactivation. Poor metabolizers (PMs) have lower concentrations of active metabolites of codeine (morphine), tramadol (O-desmethyltramadol), oxycodone (oxymorphone), and hydrocodone (hydromorphone), compared to extensive metabolizers (EMs). Morphine and O-desmethyltramadol have 200-fold greater affinity for the µ-opioid receptor than the parent compound, whereas oxymorphone and hydromorphone have 40-fold and 10-fold higher receptor affinity compared to their parent compounds, respectively. Consequently, PMs may fail to derive pain relief from these opioids compared to EMs. Interestingly, the occurrence of side effects may not differ between PMs and EMs so that while PMs may get little to no pain relief from certain opioid analgesics, they may still experience troublesome adverse effects. Intermediate metabolizers (IMs) are also expected to have reduced analgesic response based on their significant reduction in enzyme activity. Conversely, individuals with the UM phenotype may have toxic concentrations of active opioid metabolites, with reports of life-threatening toxicity and death. The µ-opioid receptor gene (OPRM1) is the primary binding site for endogenous opioid peptides and opioid analgesics, and may have additional contributions to opioid response. The investigators propose to examine the effect of CYP2D6 genotype-guided pain management on cancer pain control in study participants and the additional effect of the OPRM1 genotype on response to opioids.

This will be a randomized, open label, multi-site clinical trial conducted in UF Health Cancer Center in Gainesville, FL and in Moffitt Cancer Center in Tampa, FL. Each site will be responsible for overseeing patient care and research at their respective facility. This research will examine pain-related outcomes with CYP2D6-guided cancer pain management for study participants. In addition, the investigators will evaluate a prospective cohort study in the same population examining the effect of OPRM1 genetic variants on pain relief and adverse drug effects over time. Participants will be randomized in a 1:1 manner to receive CYP2D6 genotype-guided (n=50) or non-genotype-guided (traditional, n=50) selection of pain medication. Patients in the genotype arm will be genotyped at baseline for CYP2D6 variants. Participants will fill out the the Brief Pain Inventory-Short Form (BPI-SF) and M.D. Anderson Symptom Inventory (MDASI) questionnaires at baseline. Then, during the clinical visits the same questionnaires will be done during weeks 2, 4, 6, and 8 or by telephone or electronic survey.