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Friday, February 13, 2009

Cancer pain intensity and analgesic complexity

ResearchBlogging.orgJournal of Clinical Oncology has an intriguing paper on cancer pain intensity and 'complexity' of cancer pain management. The data come from a prospective, Canadian study of ~600 'advanced' cancer patients referred for palliative care consultation (including inpatient and hospice-based settings). 21% reported severe, at least 7/10 pain, at initial assessment. They defined pain control as pain 3/10 or less and 3 or fewer breakthrough doses for at least 3 consecutive days.

The findings are interesting on a couple levels. First is the natural history data. Median time to pain control was 4 days for patients reporting mild pain at baseline, compared to 22 days with those reporting severe pain. In fact it looks like (I say 'looks like' because this is me eye-balling a Kaplan-Meier curve) there is a group (~15% of patients with baseline moderate or severe pain) who don't achieve stable pain control (as defined above) even after 90 days. In multivariate analysis having baseline moderate to severe pain, suspected neuropathic pain, and age less than 60 years were independently associated with longer time to pain control. Psychological factors, at least how they measured them, did not predict length of time to pain control in the multivariate analysis. Increased baseline pain also predicted increased use of adjuvant analgesics and higher final opioid dose (a median of 72 vs 12 mg of oral morphine equivalents, compared with baseline mild pain patients).

Well, so what? Patients who hurt more need more meds and it takes longer to achieve decent analgesia. On its face that isn't surprising, and could seem to be quite a dull finding. It isn't necessarily however. First off this is supporting data that numeric rating scale reports do tell us something about a group of patients (ie - allow comparisons between groups of patients as opposed to only the strict interpretation of NRS data that they are meaningful only on an individual basis to compare, say, treatment response after initiating a new analgesic in an individual patient). (Yes, this has been a point of some controversy, and the paper's discussion section addresses it further if you're interesting). Second, it's supporting data that for patients who present with severe pain we should not necessarily be 'starting low and going slow' and should in fact be more aggressive. I suspect however that most of us do this anyway because it's, well, the obvious thing to do (much of the time).

Finally, however, I am left wondering about this last 15%: the ones that never achieve good control (at least as defined by the criteria above which has the major limitation of not being based in how patients themselves rate their satisfaction with their analgesia: are they happy with their pain relief? Can they do the things they want to do despite having, say, 5/10 pain, etc.?) Most of us who practice in referral cancer pain settings (that is, for example, an oncologist has to refer a patient to me for pain in order for me to see that patient) tend to get referred the patients with the toughest to control pain syndromes (intolerable side effects, lack of efficacy of multiple agents, etc.). This, then, is a patient population near and dear to my heart, and one that hasn't been studied very closely, but is actually quite central to many of us with referral-type palliative practices. Talking with others about this, it there seems to be a bi-modal distribution of patients with cancer pain: the (thankfully vast) majority who do just fine with all our 'usual moves' vs. the (thankfully) few who don't seem to gain particular benefit (whether it's in pain rating, function/mobility, mood/ability to enjoy life) from most things we do, and often with a tremendous amount of suffering tacked on (not least of which are the side effects from the treatments we prescribe). It's these few I'm particularly interested in - who they are, how we can recognize them early, why they respond differently to our 'usual moves' (yes I'm sure it's a combination of genetic, psychiatric, and otherwise neurobiologic reasons but what exactly does that mean anyway), and what we can do about it (because I wonder if they need a distinctly different approach than running them through the toolkit which happens to work for most other patients)....

So, sure, that was a rambling presentation of some thoughts that have been meandering through my mind lately, but I am hopeful that as our research base matures these questions will begin to get answered.

R. L. Fainsinger, A. Fairchild, C. Nekolaichuk, P. Lawlor, S. Lowe, J. Hanson (2008). Is Pain Intensity a Predictor of the Complexity of Cancer Pain Management? Journal of Clinical Oncology, 27 (4), 585-590 DOI: 10.1200/JCO.2008.17.1660

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