1. Susman, Ed

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PALM SPRINGS, Calif.-Lung cancer patients who have pain from other conditions before undergoing thoracotomy are more likely to experience long-term chronic postoperative pain than individuals who do not have pain prior to the surgery for early-stage disease, researchers reported here at the American Pain Society Annual Scientific Meeting.

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For the study of 43 patients, the mean pain score six months after undergoing surgery for the 18 patients who had scores greater than 5 before surgery reported scores of about 7 on the visual analog scale compared with scores of about 2 for the 25 patients who had lower scores before undergoing surgery, reported Barbara Hastie, PhD, Research and Policy Analyst at the University of Wisconsin, Madison, and Adjunct Assistant Professor of Research at the University of Florida College of Dentistry, Gainesville.


"About 42 percent of the patients had pain before they went into surgery," she said in an interview at her poster study. "It was not pain in the same area or the type of pain associated with post-surgery pain." She said that typically these patients were complaining of hip pain, lower back pain, and pain related to bouts of shingles.


"We did a lot of baseline measures for baseline pain sensitivity, psychosocial factors, genetic factors, sleep, and inflammatory markers. We expected people to have pretty high pain after the surgery. In the patients with pain before surgery, the pain level decreased until about month three and then it started to go up."



The question of why that happened in the group with pain prior to surgery but didn't in the other patients continues to be part of the research investigation. "We are looking at what factors can predict that," Hastie said.


In the acute-pain phase-the period from surgery to 14 days post-surgery, the patients who had high stressors prior to the operation had visual analog scale pain scores of about 7.5 two weeks after surgery. This group of patients had pain scores of about 5 before surgery. The group with low pain scores of about 3 prior to surgery reported that their mean pain scores dropped close to baseline 2 weeks after surgery.


"When we follow these patients out to six months, the people with low stressors before surgery had a pain level of about a 2, but the other group was still about 7.


"We are trying to figure out what we can do before surgery to reduce some of that inherent stress," she said. "Post-surgical pain could ostensibly be one of the most manageable pain conditions, given the standardization of procedures and controlled environments. However, in reality, postoperative pain trajectories reveal tremendous individual differences and vagaries of responses, making management particularly challenging.


"Research has intensified to identify factors that can predict pain course to optimize pre- and peri-operative care, improve post-surgical pain management, and halt transition to chronic pain," Hastie continued. "We are also looking to see if there are ways to treat that acute pain more aggressively to prevent it from continuing long term."


She said that the goal is to try and get all patients who undergo thoracotomy to have the reduction in pain so their quality of life can be improved. "The irony is that thoracotomy is the first-line treatment for early-stage lung cancer, with the implication that patients who survive this invasive procedure are disproportionately affected by chronic pain secondary to the life-saving treatment.


"Thoracotomy patients could benefit greatly from such optimistic endeavors since reportedly up to 60 percent of patients experience chronic pain of moderate to severe nature as long as four to five years after surgery."


The putative factors implicated in the development of chronic pain are further complicated by a highly individualized constellation of responses such as responses to medication and surgical insult, she explained. "The immune system and inter-relationship with inflammatory and stress responses have received less attention but are integral to systemic reactivity, recovery, and homeostasis. Indeed, pain is not immune from being affected by these forces, and arguably its trajectory is influenced by and inter-related to these factors."


'Pain Begets Pain'

Asked for his assessment, Roger Fillingim, PhD, a past president of the American Pain Society, said: "In general there is a lot of interest in understanding what predicts the development of chronic pain or the transition from acute to chronic pain. It is known that a significant proportion of patients after thoracotomy will develop chronic pain. But the reasons for that are not very well known."


Fillingim, also Professor of Community Dentistry and Behavioral Science at the University of Florida, added:"In the general population, pain before surgery has been a risk factor for pain after surgery. Pain begets pain. If you identify people who had pain before surgery, they are more likely to have pain after surgery."


He also suggested other factors that could be responsible for the continuation of pain in the vulnerable patients. "There might be genetic risk factors for development of pain in general. They may have a different genotype that alters the way their brain processes pain. That is a possibility," he said. "They may have had previous life experiences that could have changed their body or their brain, for example, putting them at risk for pain after thoracotomy.


"There also may be some kind of environmental exposure that occur in people who are at genetic risk for pain, and those people when they experience further exposures-and surgical injury would be another exposure-they are likely to have even more pain," he said.


Further Analysis

Hastie said that her research team is analyzing the data to try to unravel the genetic and pharmacogenetic mysteries that predispose patients to chronic pain.


The 43 subjects in the study were selected preoperatively from the University of Florida Thoracic and Cardiovascular Surgery Clinic. All subjects underwent extensive baseline assessment about one to two days prior to open thoracotomy, all performed by the same surgeon.


There were 21 men and 22 women in the study, and their mean age was 64.2. About 90 percent were non-Hispanic whites; the rest were African American. A smoking history was acknowledged by 11 of the patients; 24 of the patients (55.8%) were diagnosed with non-small-cell lung cancer. About 83 percent of the patients were diagnosed with Stage 1 cancer, and the others had Stage 2.


"Although this is a small sample and caution must be exercised in interpreting the results, they do suggest the importance of considering possible interventions to preemptively reduce surgical stress and potentially regulate immune and inflammatory responses to improve recovery and reduce the incidence of chronic post-thoracotomy pain."