An international multicentre validation study of a pain classification system for cancer patients☆
Introduction
Pain is one of the most prevalent and distressing symptoms in patients with advanced cancer. Approximately 70% of these patients will experience pain at some point during the progression of their disease.1 Although most patients achieve adequate pain control,2, 3 some – particularly patients with more complex pain syndromes – fail to obtain satisfactory analgesia. For these patients, clinicians may need to adopt a more intense and complex programme of therapeutic intervention, and as a result, more time is often required to achieve adequate pain control.4
Standardised approaches for assessing and classifying cancer pain need to be developed to identify and treat patients with complex pain syndromes. However, the complex, multidimensional nature of cancer pain presents unique challenges for pain classification. A review of the cancer pain literature has revealed the difficulty in comparing research results of analgesic management for cancer pain, due to the lack of a standardised approach.5 Diverse interpretations of the pain experience, as well as many factors that may contribute to it, have impeded the development of a standardised classification system. Although better characterisation and classification of pain syndromes would allow for more valid clinical and research comparisons, there is no universally accepted pain classification tool.6, 7
The development of a standardised classification system that is comprehensive, predictive of difficulty in achieving analgesia and simple to use could provide a common language for the clinical management and research of cancer pain. Bruera and colleagues recognised the need for such a system, prompting the development of the Edmonton Staging System (ESS).8, 9 The ESS has been used in a number of reports where it was found useful in describing the underlying cancer pain syndrome.10, 11, 12, 13, 14, 15, 16 Interpretational difficulties with analgesic prognosis and feature definitions have limited the international acceptance of the ESS. To overcome these limitations, an expert panel, consisting of physicians and researchers in the Edmonton Regional Palliative Care Program, developed the revised Edmonton Staging System (rESS). We have subsequently conducted five validation studies: a pilot study, a regional multicentre study,17 secondary analysis looking at pain intensity,18 opioid escalation19 and a construct validation study for validating definitions using an expert panel.20 Based on feedback generated by the latter study and to reflect the intended use as a classification system, the amended instrument was renamed the Edmonton Classification System for Cancer Pain (ECS-CP).21 The ECS-CP includes five features – pain mechanism, incident pain, psychological distress, addictive behaviour and cognitive function (Appendix A). These features and the definitions and guidelines for use are the basis of the ECS-CP (Appendix B).
Using the revised definitions for the ECS-CP pain features,21 the primary objective of this study was to assess the predictive validity of the ECS-CP as a tool for classifying cancer pain in a diverse international sample of patients, who were referred to palliative care services. Our hypothesis was that patients with more problematic pain features, as classified by the ECS-CP, would require a longer time to achieve stable pain control, require more complicated analgesic regimens and use higher opioid doses than patients with less complex pain syndromes.
Section snippets
Methods
A total of 1100 consecutive patients were recruited from 11 palliative care sites in Canada, the United States, Ireland, Israel, Australia and New Zealand (100 patients per site). The selection of these sites was purposeful, being limited to locations providing specialist palliative care services, such as a palliative consult service (inpatient and outpatient), tertiary palliative care unit or hospice setting. At study entry, a palliative care specialist (physician or nurse consultant)
Results
Demographic and clinical characteristics of the 1100 patients included in the study are listed in Table 1. Of these, 944 (86%) had a pain syndrome. The patients with a pain syndrome were significantly younger (p < .001), less likely to have lung cancer (p = .03) and more likely to have genito-urinary cancer (p = .01) than the patients with no pain syndromes. Fifty percent of patients with a pain syndrome (n = 478) achieved stable pain control. The remaining patients had either died (n = 160, 17%) or had
Discussion
The results of this international multicentre study confirm the findings of our previous research: neuropathic pain, incident pain, psychological distress, addictive behaviour and moderate to severe pain intensity are significant predictors of complexity of pain management as measured by the outcomes of longer duration (days) to achieve stable pain control, the use of more adjuvant treatments and the use of higher opioid doses. As noted previously17 these findings reflect clinical practice, in
Conclusion
The ECS-CP is a simple, comprehensive categorical classification system for meaningfully assessing cancer pain. While many factors have been proposed as prognostic for pain control, the ECS-CP is the first pain classification system to simultaneously integrate these factors within a cohesive framework. The items included in the ECS-CP represent only initial efforts to define a standard core of variables, and additional items such as analgesic tolerance, genetic variations and age would be
Conflict of interest statement
None declared.
Acknowledgements
We thank colleagues who assisted with patient assessments and/or data collection: Carla Stiles, Audra Arlain, Laureen Johnson, Donna deMoissac, Lorelei Sawchuk, Viki Muller, Hue Quan, Pablo Amigo, Doreen Oneschuk, Bei Pei, Gayle Jones, Tonya Edwards, B.J. Clayton, Jenny Thurston, Vina Nguyen, Larry Hasson, Kate McLoughlin.
Robin Fainsinger, Neil Hagen and Cheryl Nekolaichuk are supported by the Canadian Institutes of Health Research through grant support for the CIHR New Emerging Team in
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Presentation list: Fainsinger R, Nekolaichuk C, Lawlor P, et al. An International Multicentre Validation Study of a Pain Classification System for Advanced Cancer Patients. Oral Presentation at the 11th Congress of the European Association for Palliative Care, Vienna, Austria, 10th May 2009.