Challenges in cancer pain management--bone pain.
Whilst not strictly a neuropathic injury, cancer-induced bone pain (CIBP) is a unique state with features of neuropathy and inflammation. Recent work has demonstrated that osteoclasts damage peripheral nerves (peptidergic C fibres and SNS) within trabeculated bone leading to deafferentation. In addition, glia cell activation and neuronal hyperexcitability within the dorsal horn, are all similar to a neuropathy. Gabapentin and carbamazepine (both anti-convulsants that modulate neuropathy) are effective at attenuating dorsal horn neuronal excitability and normalizing pain-like behaviours in a rat model of CIBP. However alterations in neuroreceptors in the dorsal horn do not mimic neuropathy, rather only dynorphin is upregulated, glia cells are active and hypertrophic and c-fos expression is increased post-noxious behavioural stimulus. CIBP perhaps illustrates best the complexity of cancer pains. Rarely are they purely neuropathic, inflammatory, ischaemic or visceral but rather a combination. Management is multimodal with radiotherapy, analgesics (opioids, NSAIDs), bisphosphonates, radioisotopes and tumouricidal therapies. The difficulty with opioids relates to efficacy on spontaneous pain at rest and movement-related pain. Potential adjuvants to standard analgesic therapies for CIBP are being explored in clinical trials and include inhibitors of glutamate release.
Colvin
L
L
Department of Anaesthesia, Edinburgh Cancer Research Centre, St Columba's Hospice Chair of Palliative Medicine, Institute of Genetics & Molecular Medicine, Western General Hospital, Crewe Road South, Edinburgh, UK.
Fallon
M
M
D000700:Analgesics / Q000627:therapeutic use; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000627:therapeutic use; D050071:Bone Density Conservation Agents / Q000627:therapeutic use; D001847:Bone Diseases / Q000517:prevention & control*; D001859:Bone Neoplasms / Q000150:complications*; D004164:Diphosphonates / Q000627:therapeutic use; D004333:Drug Administration Routes; D019332:Endothelin-1 / Q000037:antagonists & inhibitors; D006801:Humans; D008012:Lidocaine / Q000627:therapeutic use; D016202:N-Methylaspartate / Q000037:antagonists & inhibitors; D053244:Osteoprotegerin / Q000627:therapeutic use; D010146:Pain / Q000517:prevention & control*; D019030:Receptors, Vitronectin / Q000037:antagonists & inhibitors
D000700:Analgesics; D000894:Anti-Inflammatory Agents, Non-Steroidal; D050071:Bone Density Conservation Agents; D004164:Diphosphonates; D019332:Endothelin-1; D053244:Osteoprotegerin; D019030:Receptors, Vitronectin; C094340:integrin alphavbeta1; D016202:N-Methylaspartate; D008012:Lidocaine