Evaluation of the comparative analgesic effectiveness of transdermal and oral opioids in cancer patients: a propensity score analysis.
BACKGROUND
Transdermal delivery systems containing fentanyl or buprenorphine, despite the relatively lack of comparative studies, have reached an impressive share of the market in several countries. In the context of a wider observational study, we applied the propensity score to test the comparative effectiveness of the two routes of administration (oral vs. transdermal).


METHODS
We applied the propensity score in a subgroup of patients (starting the World Health Organization third step therapy during the scheduled follow-up of 28 days) using pre-planned primary (pain intensity change) and secondary endpoints, such as increase in doses, need for switching and safety profile. Univariate and multivariate analyses were carried out.


RESULTS
Three-hundred sixty-six eligible cases were analysed. We found a difference among the two groups in terms of variables potentially associated with therapy choice and outcomes. After adjusting for propensity score, results were in favour of transdermal delivery systems for the primary endpoint (odds ratio 1.68; p = 0.04). A similar trend was also present for the other secondary endpoints. Only in the case of nausea and vomiting, patients receiving transdermal delivery systems reported a higher frequency of events.


CONCLUSION
The application of the propensity score has helped understand better the actual effectiveness of transdermal delivery systems that are at least equivalent to the oral opioids, and even more effective for pain intensity reduction.