Advances in cancer pain management

Extensive experience suggests that cancer pain can be relieved in 80 % to 90% of patients using a simple opioid-based analgesic regimen [1–4]. For most patients, a satisfactory outcome follows an opioid dose adjustment period that culminates in a favorable balance between analgesia and side effects. In some cases, however, this favorable balance between analgesia and side effects cannot be achieved or maintained over time. Pain cannot be controlled with dose escalation because of moderate to severe opioid-related side effects. This kind of pain may be considered ‘‘poorly responsive’ ’ to the opioid. Poor opioid responsiveness is an important clinical phenomenon; the management of which requires careful assessment and working knowledge of a broad range of therapeutic options. This article describes some of the possible mechanisms underlying poor opioid responsiveness and the clinical strategies that might be considered to improve the balance between analgesia and side effects. Those interested in a more detailed synopsis of current strategies for treating cancer pain and the mechanisms underlying poor opioid responsiveness are referred to the following reviews [5–9]. Definition of opioid responsiveness Opioid responsiveness has been defined as the degree of analgesia achieved as the dose is titrated to an endpoint defined by intolerable side effects. If analgesia is generally inadequate because side effects impose a practical limit on dose escalation, the pain may be said to be relatively poorly responsive to the specific drug and route of administration. If a favorable balance between analgesia and side effects can be attained, the pain may be said to be relatively responsive to the drug and route