Predictors of long-term opioid effectiveness in chronic non-cancer pain patients attending multidisciplinary pain treatment clinics : a Quebec pain registry study

Objective: This study aimed at identifying characteristics of individuals who are most likely to benefit from long-term opioid therapy in terms of reduction in pain severity and improved mental health-related quality of life (mQoL) without considering potential risks. Methods: This was a retrospective cohort study of 116 patients (age=51.3 ±12.5 years, male=42.2%) enrolled in the Quebec Pain Registry between 2008 and 2011 and who initiated opioid therapy after their first appointment in a multidisciplinary pain clinic and persisted with this treatment for at least 12 months. Clinically significant improvement was defined as a 2-point decrease on the PEG 0-10 Scale of pain severity at 12-month follow-up and a 10-point increase on the SF-12v2 Mental Health-Related Quality of Life Summary Scale which corresponds to one standard deviation of the mean in the general population (Mean = 50, SD = 10). Results: Clinically significant reduction in pain severity was observed in 26.7% of patients while improvement in mQoL was reported by 20.2% of patients on long-term opioid therapy. Older age (OR=1.04 (95% CI: 1.0 – 1.08), p=0.032) and alcohol or drug problems (OR=0.26 (95% CI: 0.07 – 0.96), p=0.044) were weakly associated with pain severity at 12-month follow-up. Baseline higher pain severity (OR=0.62 (95% CI: 0.43 – 0.91), p=0.014) and baseline higher mQoL (OR=0.89 (95% CI: 0.83 – 0.95), p=0.001) were associated with non-improvement in mQoL. Conclusion: The analysis failed to identify clinically meaningful predictors of opioid therapy effectiveness making it difficult to inform clinicians about which CNCP patients are most likely to benefit from long-term opioid therapy