BETHESDA, MD—Because chronic pain remains a major clinical problem and is highly variable, individualizing pain treatments for patients was emphasized here at the National Institutes of Health Pain Consortium's Symposium. This fifth annual meeting of the multi-institute, multi-disciplinary pain consortium, of which the National Cancer Institute is a member, has mushroomed in both attendance and participation by researchers every year.
The day may come when personalizing pain treatment according to individual pain phenotype and individual pain genotype will become a reality, suggested Clifford J. Woolf, MD, PhD, Professor of Neurology and Neurobiology at Harvard Medical School and Children's Hospital. “Because we now realize that the old assumption that pain is pain is pain is incorrect, we need to develop tools that capture relevant information about an individual patient's pain that can drive treatment decisions,” he said.
Research studies are now helping to identify patients who are at higher risk for postsurgical pain, said Robert R. Edwards, PhD, Clinical Psychologist in the Department of Anesthesiology, Pain Management Center, at Brigham & Women's Hospital and Harvard Medical School.
“In general, individual differences in the severity and persistence of postoperative pain are large and tend to be unrelated to surgical variables. For example, conservative breast surgery such as lumpectomy results in approximately the same rates of chronic pain as does mastectomy, a surgery that produces substantially more tissue damage.”
Dr. Edwards said the variables that have been identified as potential predictors of risk for long-term pain after surgery can be demographic, anatomical, neurophysiological, and psychosocial. When physicians know what these risk factors are, he said, the hope is that individualized therapies can be given to reduce the likelihood of postsurgical pain in patients.
Persistent Pain After Surgery
The following are potential risk factors for persistent postsurgical pain, he noted:
- Pain in other areas of the body before the operation, which can confer a three-fold higher risk for post-operative pain.
- High levels of psychosocial distress such as anxiety before the operation.
- Smoking, which can double the risk of postoperative pain, apparently through a pain-hypersensitivity mechanism.
- Poor quality of sleep, such as sleep-onset insomnia and sleep disruption.
- Being a chronic user of opioid drugs.
- Catastrophizing and/or inflammatory reactivity, which is linked to such tendency to express negative thoughts and emotions and exaggerate the impact of painful experiences. (At the annual scientific meeting of the American Pain Society, held just after the NIH Pain Consortium meeting, Francis J. Keefe, PhD, Professor of Psychiatry and Behavioral Sciences and Associate Director for Research in the Duke Pain and Palliative Care Initiative, said in a talk that he considered catastrophizing to be a key to understanding disease-related chronic pain in patients.)
Asked by OT if patients should be routinely and systematically assessed for the risk of persistent postsurgical pain before an operation, such as cancer surgery, Dr. Edwards said, “We're probably not at that point yet. We need some more predictive work” before a pain-risk profile can be used clinically.
But he said, as a first step, physicians could benefit from better professional education on the risk factors that lead to long-term pain. Asked about the problem of suggestibility in a presurgical pain-risk profile assessment tool, should one be used clinically, Dr. Edwards said, “That will be a very substantial issue going forward.” But, he said, education of the presurgical patient about pain would be better than no education, and patients would not have to think that long-term postsurgical pain was all in their heads.
Cluster of Symptoms Linked to Chronic Cancer-Related Pain
In a sample of patients with different cancers, those experiencing chronic pain tended to score high on a cluster of symptoms including fatigue, sleep disturbance, and depression and tended to be younger, said Christine Miaskowski, RN, PhD, FAAN, Professor in the Department of Physiological Nursing, Associate Dean for Academic Affairs and holder of the Sharon A. Lamb Endowed Chair in the School of Nursing at the University of California at San Francisco.
“Inter-individual variability in pain severity and responses to analgesic medications is the exception rather than the rule,” noted Dr. Miaskowski, who is the first nurse to be awarded an American Cancer Society Clinical Research Professorship and is now conducting a randomized clinical trial to evaluate the effects of two different levels of a psycho-educational intervention to improve cancer pain management.
Asked by OT if the younger cancer patients might have had a higher symptom cluster burden in part because of stress caused by competing demands, such as holding down jobs while raising young children, Dr. Miaskowski said that could be a factor.
“The idea is to try to tease out the predictors” of chronic pain in those with a high burden of symptoms, she said, noting that these predictors probably include psychological, environmental, and genetic factors.
Ideally, she said, it would be helpful to intervene to help such high-risk patients with both counseling and new drugs. “It's not going to be one single thing,” she said of a potential intervention to help patients at high risk for chronic pain.
Results of a pilot study reported at the NIH pain research meeting reinforce the finding that presurgical risk factors can predict persistent postsurgical pain. In a study of 77 patients who underwent five different surgical procedures, including radical mastectomy and lumpectomy, patients were assessed before their operations to see if psychological factors would have an influence on postsurgical pain, said lead author Ian Carroll, MD, MS, Assistant Professor in the Department of Anesthesiology at Stanford University School of Medicine's Pain Management Center.
Dr. Carroll found that the symptoms of post-traumatic stress, self-perceived susceptibility to addiction, and elevated levels of postoperative day-one pain severity were all risk factors predicting delayed pain resolution even after controlling for other variables. In this study, the mean time to pain resolution was 64 days, and 21% of patients reported ongoing pain at the surgical site 150 days after the operation.
Finally, the accuracy of a pain assessment can be influenced by how well a physician communicates with a patient about his or her pain concerns, according to a study of 19 oncologists and 20 family physicians treating patients with advanced-stage cancer.
Lead author Cleveland Shields, MD, PhD, Associate Professor of Child Development and Family Studies at Purdue University, studied pain assessment among the participating physicians using hidden audio recording devices at patient visits. Physicians who elicited and validated the cancer patients' concerns about pain with an anxious voice tone (emphasizing patient-centered communication and indicating concern on their part) were found to more adequately assess the cancer patients' pain than physicians whose tone of voice and use of language were perceived by patients to show less concern and to be less validating of their pain.