Should the rate of opioid dose escalation be included as a feature in a cancer pain classification system?

The purpose of this study was to assess the need for opioid dose escalation as a feature of a pain classification system for advanced cancer patients. Opioid dose escalation was included as a prognostic feature in the original Edmonton Staging System (ESS) for pain classification, but was not included among the five features of the revised ESS (rESS): pain mechanism, incident pain, psychological distress, addictive behavior, and cognitive function. Mercadante et al.'s definition of opioid escalation index percentage (OEI%) has been used as a surrogate marker for opioid responsiveness. Our hypothesis was that younger age (<60 years), neuropathic pain, incident pain, psychological distress, and addictive behavior would be associated with an OEI% >5%. Using data from a recent multicenter validation study of the rESS, a secondary analysis of a subsample of 532 advanced cancer patients with a pain syndrome was conducted. Approximately 44% (n=232) of the patients had an OEI% >5%. There were no significant associations between OEI% and age, neuropathic pain, incident pain, psychological distress, or addictive behavior. As originally proposed as a clinical marker, the OEI% may oversimplify the complexity of pain management in advanced cancer patients. Future studies are required to better elucidate the need for opioid dose escalation as a feature of a cancer pain classification system.