A Phase II Study About Efficacy and Safety of the Continuous IntraVenous Infusion of Ketamine as Adjuvant to Opioids in Terminally Ill Cancer Patients With Refractory Cancer Pain (CIVIK Trial)

Background: Ketamine has been used to control refractory cancer pain as an adjuvant to opioids. We conducted a prospective phase II study to investigate the efficacy and safety of 5-day continuous intravenous infusion (CIVI) of Ketamine in terminally ill cancer patients with refractory cancer pain. Methods: Hospitalized terminally ill cancer patients with refractory cancer pain were enrolled. Refractory cancer pain was indicated by requirements for 4 or more rescue opioids or pain intensity using numerical rating scale > personalized pain goal (PPG) despite of intravenous morphine equivalent daily dose (IV MEDD) ≥ 120 mg/day. The CIVI of ketamine was increased from.05 mg/kg/hour to.5 mg/kg/hour by.05 every 8 hours if pain intensity exceeded PPG or if number of rescue opioids ≥2 during prior 8 hours was required. The primary end-point was overall pain response rate, which indicates complete response (both rescue opioid ≤3/day and pain intensity ≤ PPG) plus partial response (rescue opioid ≤3/day), without unacceptable toxicities. Results: Among 21 eligible patients enrolled between September 2019 and January 2023, 20 were analyzed. Most pain mechanisms were mixed type (n = 15, 75%), with neuropathic component (n = 17, 85%). The baseline background opioids were IV MEDD 186 mg/24hour (range, 124-592), number of rescue opioids was 6 (IQR, 5-9), and median PPG was 4 (IQR, 3-4). The overall pain response rate was 50% (n = 10) including 40% (n = 8) for complete pain response and 10% (n = 2) for partial pain response. Conclusion: This study showed efficacy of gradually increasing CIVI of ketamine for terminally ill cancer patients with refractory cancer pain. CIVI of ketamine could be a useful tool in these patients considering the limited treatment options. (NCT03362073, Initial Release: November 15, 2017).