Chronic pain: cancer: opioids
Unlike benign pain, usage of opioids in chronic pain management elicits little controversy. Nevertheless, there is significant disagreement in drug choice, timing, and dosage leading to significant practice variance. In one large series, 95% of patients with advanced cancer have pain, only 50% report that it is well treated and 25% were rated as having died in severe pain. Treatment is directed at the cause of the pain, if known. Pain can be caused from a direct tumor effect (invasion causing visceral pain, bony metastasis), from treatment (neuropathic pain from chemo) or preexisting pain exacerbated from the disability of cancer and/or its treatment.
Opioids are a mainstay of cancer pain treatment but should be used in a multimodal approach which may include pharmacologic adjuncts (NSAIDs, corticosteroids, anti-convulsants, bisphophonates, etc), non-pharmacologic interventions (PT, TENS, acupuncture, supportive psychotherapy, cognitive-behavioral interventions, etc) and invasive interventions where appropriate (spinal cord stimulators, intrathecal pumps, neurolytic blocks, etc). Estimates suggest that 90% of chronic cancer pain can be treated with simple interventions.
Like all pain management, initial therapy should be conservative, but with a lower threshold for beginning narcotics. With end-stage disease upward titrations are often swift. Best therapy is usually achieved with long acting agents (Sustained release oral morphine, methadone, Oxycontin, fentanyl patches). Shorter-acting medications (oxycodone, trans-buccal fentanyl) should be provided for breakthrough.
Severe uncontrolled cancer pain is a medical emergency. If patients have failed oral therapy, inpatient or home/hospice parental therapies are used, typically IV but sometimes with SQ infusion pumps. Home PCA can have basal rates set with on-demand dosing. For many with severe untreated pain, intraspinal opioids, particularly for those with excessive side effects from oral/iv forms, is an attractive option. Infusions can be mixed with local anesthetics, clonidine and/or baclofen for synergistic effects. Because implants come with their own set of complication (bleeding, infection, equipment failure) and high costs, they are usually reserved for those judged to have at least 3 months to live.
Addictive behavior (drug craving/seeking, behavioral problems) is rare in cancer patients.