Objective. This analysis, carried out in the context of a wider observational prospective study, tried to explore whether four World Health Organization/step-III opioids (morphine, oxycodone, fentanyl, and buprenorphine) had different effectiveness when using several different outcomes and endpoints.
Design. Cross-sectional and longitudinal design.
Setting. Oncologic, palliative, and pain centers in Italy.
Patients. Two hundred fifty-eight cancer patients monitored over a 3-week follow-up program.
Intervention. Not applicable.
Outcome Measures. The analgesic efficacy was assessed using effectiveness endpoints, such as pain intensity, pain intensity difference (PID), proportion of nonresponders (NR) and full-responders (FR) subjects, percentage of switches and dose escalation.
Results. Mean values of PID led to differences among opioids ranging from 10% to 30%. FR (PID ≥ 30%) were more frequent in buprenorphine-fentanyl-oxycodone groups than in morphine; NR (PID ≤ 0%) were variable. The percentage of switches resulted three times more frequent when using morphine than buprenorphine (24.4% vs 8.6%). An increase of dose ≥5% a day was observed in 33.3% of fentanyl patients vs 15% of buprenorphine. As a whole, opioids show some different behaviors on the basis of the considered endpoints.
Conclusions. The observed results, even if the small sample size and the nature itself of the study do not allow a definitive evaluation of the effectiveness of the drugs, underline a degree of variability among opioids and address toward a correct planning of a comparative randomized clinical trial that is now underway in Italy. For this reason, a confirmative effectiveness randomized controlled trial is required.