Wednesday, September 5, 2007

When is cancer pain not cancer pain?

This question is generated by two recent articles, the new Washington State opioid-prescribing guidelines, and a statement attributed to Kathy Foley in her presentation at the NIH conference on pain and addictions in March: “Distinctions that we make about cancer pain and noncancer pain are rather arbitrary. Opiate receptors don’t know if a patient has cancer or doesn’t have cancer.” (Seen in a hard copy-only publication called PainReporter underwritten by Alpharma)

It has been common in the past to distinguish cancer (or “malignant”) pain from “benign” (as if there were such a thing) chronic pain. That paradigm, always suspect, is now becoming obsolete as a growing number of people survive cancer but with a significant burden of pain. Burton et al provide an excellent overview of the problem of pain in cancer survivors, pointing out both prevention and treatment strategies, including borrowing from the noncancer pain experience.

Jane Ballantyne has a thoughtful article (which is therefore sure to generate controversy) on the need to re-think treatment of chronic cancer-related pain, now that cancer is becoming a chronic condition with the potential for long-term survival for an increasing number of patients. She reviews the history of cancer pain treatment with opioids, recalling the difficulty pain management advocates had 20+ years ago trying to convince clinicians and patients alike that use of opioids is an important and low-risk intervention for severe pain. (The sometimes non-so-subtle message sometimes became “they’re going to die anyway, so why worry about addiction?”) Well, maybe now we do need to worry, says Ballantyne, who advocates using the same risk-reduction practices with cancer survivors as are suggested for people with chronic noncancer pain. Strikes me as very reasonable. I take issue with a point she makes a couple of times: that chronic exposure to opioids produces “inevitable” changes in the brain which have been associated with addictive behaviors. She is undoubtedly better versed in that science than I am, but I don’t see the same inevitability that she does. Certainly the changes in the brain, if universal, are insufficient to “cause” addiction, which is manifested by a collection of behaviors which are relatively rare.

Ballantyne and other responsible commentators point out that no one knows the incidence of addiction among people with chronic pain of any etiology (because no one has done that study and published estimates are often based on pain clinic populations, hardly a representative sample of the universe of people with persistent pain), that the risk is low for an individual without multiple risk factors, and that simple exposure to an opioid does not “cause” addiction.

I should point out that Ballantyne distiguishes between a palliative care model for patients with progressive and especially end-stage disease, and those with pain but a prolonged prognosis. She expresses concern that a shifting pradigm for cancer pain management has the potential to victimize patients with end-stage disease who may need aggressive pain treatment with opioids.

By the way, this entire issue of Current Pain & Headache Reports is devoted to cancer pain.

The Washington State Guidelines have generated controversy for suggesting a ceiling of 120 mg of morphine per day for people with chronic noncancer-related pain. A referral to a pain specialist (undefined definition, but only 11 listed for the entire state) is recommended for patients needing more than 120 mg/day. Long-term cancer survivors (undefined) with chronic pain would be included under the treatment guidelines. The American Pain Society has cited concern about the care of patients with cancer-related pain under these guidelines.

A related topic (sort of—some people will relate them too closely) is the treatment of pain in end-stage disease in patients who have addictive illness. At this year’s AAHPM Ron Crossno gave a presentation about this. Among other things, he said something like: “If you haven’t seen any patients who are abusing some substance, it’s because you’re not paying attention.” Steve Passik and colleagues have a couple of articles (here and here) and Passik & Russ Portenoy have a book chapter on this topic (2nd edition of Principles and Practice of Palliative Care and Supportive Oncology; I don't think it carried over to the 3rd ed.).

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