Use of rescue opioids and pain control after ketamine initiation in refractory cancer pain: A multicentric observational study

BackgroundRefractory cancer pain (RCP) affects 10-20% of cancer patients, exhibiting limited response to standard opioids (OPI). Ketamine (KET), an anesthetic medication, has gained recent attention for its potential in managing RCP. This study aims to describe the consumption of rescue OPI before and after initiating KET, the rate of patients meeting a controlled pain criteria, and its safety profile.MethodsA prospective observational study was conducted in three academic hospitals. Over an 18-month period, we included all cancer patients who initiated KET therapy based on the criteria of their treating medical team. The frequency of OPI rescues was recorded on days five (D-5) and two (D-2), and on days two (D+2) and five (D+5) pre and post KET initiation, respectively. Controlled pain criteria were defined as a 72-hour interval with no more than 3 OPI rescues per day, absence of breakthrough pain, and no escalation in OPI dosage. All adverse effects (AEs) were recorded in accordance with the CTCAE 5.0 guidelines.ResultsFifty-two patients were included, and their characteristics are described in the table. The most common initiation dose of KET was 0.5 mg/kg/day orally (71.2%). Median oral morphine milligram equivalent (MME) at initiation of KET was 120mg. Overall survival from the onset of KET therapy was 43 days. Median daily OPI rescue was 3.90 on D-5 and 4.62 on D-2, decreasing to 2.79 on D+2 and 2.77 on D+5 (p=<0,05). Sixty-one percent of patients met the criteria for controlled pain. Seventeen AEs in twelve patients (23%) were recorded, with confusion (7.6%) and sleep disturbance (5.7%) being the most common. Grade 3 AE occurred in two patients (3.8%), with no grade 4-5 AEs reported. Table: 1479P Characteristics n (total) n (%) Total patients 52 100% Male 33 53.2% Female 19 36.5% History of heart disease 6 11.5% History of psyquiatric disease 6 11.5% Cancer histology Lung 9 17.3% Urothelial 9 17.3% Colon 7 13.5% Others 27 51.9% Opioid at ketamine initiation Metadone 27 51.9% Morphine 18 34.6% Fentanyl 6 11.5% Oxycodone 1 1.9% Oral morphine milligram equivalent (MME) at Ketamine initiation <100mg 23 44.2% 100-300mg 16 30.7% >300mg 13 25% Starting Ketamine dose (per day) 30mg 35 67.3% 45mg 10 19.2% Others 7 13.4% Administration route Oral 37 71.2% Subcutaneous 14 26.9% Intravenous 1 1.9% Maximum ketamine dose received 0.5mg/kg/day 28 53.8% 1mg/kg/day 10 19.2% 1.5mg/kg/day or more 14 21.2% ConclusionsA significant decrease in rescue opioids usage was observed after initiating ketamine. Over 60% of the patients met the criteria for controlled pain, with a favorable safety profile. Further comparative studies are required to better understand the role of ketamine in cancer pain.Legal entity responsible for the studyVall d'Hebron University Hospital.FundingHas not received any funding.DisclosureAll authors have declared no conflicts of interest.