Source: www.medscape.com
Author: Fran Lowry

Patients with cancer who continue to smoke despite their diagnosis experience greater pain severity than their counterparts who quit or who have never smoked, according to new research published in the January 2011 issue of Pain.

Not only is their pain more severe, but it interferes more with their activities of daily living, lead author Joseph W. Ditre, PhD, a clinical psychologist at Texas A & M University in College Station, told Medscape Medical News.

“Many smokers, when they get cancer, feel that smoking is one of the only pleasures they have left to them and refuse to quit,” he said in an interview. “But our research suggests that quitting has definite benefits. It’s one more thing that doctors can tell their patients to help them stop smoking.”

Continued smoking has been associated with an increased risk of developing a second primary tumor, reduces the effectiveness of treatment, and is associated with poorer survival rates, Dr. Ditre said. “The subtext for this is that smoking can also worsen cancer-related symptoms and treatment side effects, such as pain and fatigue.”

“About 75% of people with advanced-stage cancer report moderate to very severe pain, so it is a very big factor in terms of the disease course, and yet there is surprisingly little research on this topic,” he added.

Dr. Ditre, who led this work while he was earning his doctorate at the University of South Florida and Moffitt Cancer Center in Tampa, told Medscape Medical News that the aim of his research was to examine the association with pain across diverse cancer types with regard to potential benefits of quitting smoking.

“Smoking is known to decrease oxygen, and there is also a possibility that tobacco smoke over time has some type of direct influence on the neurological processing of sensory information, and so may actually change the way pain receptors operate,” he said. “There are many potential mechanisms, and this is something that is under study.”

More Smoking, More Pain
In the current study, Dr. Ditre and colleagues looked at the association between multiple levels of smoking status and several pain-related outcomes in a sample of 224 patients who were about to begin chemotherapy for a variety of cancers, including breast, lung, bladder, ovarian, colon, head and neck, testicular, endometrial, prostate, and rectal/anal cancers; mesothelioma; and sarcoma.

The patients were part of a larger study investigating the efficacy of 2 interventions — stress management and exercise training — for improving quality of life during chemotherapy. Ten percent of patients had stage I disease, 26% had stage II, 30% had stage III, and 34% had stage IV.

The patients self-reported their smoking status and cigarette consumption at study entry. Patients who reported smoking more than 100 cigarettes in their lifetime were defined as smokers, and never-smokers were defined as smoking fewer than 100 cigarettes.

Smokers were further defined as former smokers (those who had quit smoking and had not smoked any cigarettes in the past month) and current smokers (those who reported having smoked in the past month). Current smokers were also asked how many cigarettes they currently smoked per day.

The patients used the Medical Outcomes Survey 36-item Short Form Body Pain subscale, rating their perceived severity of bodily pain on a scale of 1 to 6, where 1 indicated “none” and 6 indicated “very severe,” and the degree to which pain interfered with their daily routine on a scale of 1 to 5, where 1 indicated “not at all” and 5 indicated “extremely.”

They also rated their distress on the Memorial Symptom Assessment Scale-Short Form, where 0 indicated no distress at all and 4 indicated the most stress.

Current smokers reported experiencing significantly more severe pain than never-smokers and greater interference from pain than former smokers or never-smokers.

In addition, there was also an inverse relation between pain severity and the number of years since quitting: The longer it had been since a patient had quit smoking, the less pain that patient reported.

Dr. Ditre stressed that the findings are correlational and do not point to a direct cause between smoking and cancer pain. In fact, the direction of causality is unclear. “You cannot infer exactly what is causing what, only that they are connected in some way,” he said.

“Smoking may be increasing the pain that these cancer patients are experiencing, or another possibility is that their pain may have caused them to continue smoking. It could be one way or the other,” he noted. “In fact, we’ve done work with noncancer populations in which we have demonstrated that pain is a significant motivator of smoking behavior. People who experience pain have a greater desire to smoke and will be more motivated to smoke, and will smoke more.”

Whether or not there is a causal relationship, it is important for patients with cancer to realize that smoking appears to be worsening their pain, he said.

“Doctors can tell their patients that they now have information that suggests that if you stop smoking you may experience less pain than you would otherwise, although we are not 100% sure yet why that is,” Dr. Ditre said.

Research Needed to Understand Mechanisms
In an accompanying editorial, Lori Bastian, MD, from Duke University and Durham Veterans Affairs Medical Center in North Carolina, writes that the findings by Dr. Ditre and his team are consistent with those of other studies and that they have public health significance.

“Clinicians must do more to assist cancer patients to quit smoking after their diagnosis,” Dr. Bastian writes. “If pain increases the urge to smoke, a formal smoking cessation program for cancer patients should also include efforts to control pain severity.”

She concludes that more research is needed to understand the mechanisms that relate nicotine to pain and that prospective longitudinal studies should be performed to clarify “the issue of directionality, demonstrate no harm, and determine the impact of smoking cessation on pain severity among cancer patients.”

Source:
Pain. 2011;152:10-11, 60-65. Abstract

Note:
1. This study was supported by funding from the American Cancer Society and the National Institute on Drug Abuse. The study authors have disclosed no relevant financial relationships. Dr. Bastian is supported by grants from the Department of Veterans Affairs, Health Services Research and Development, and the National Institutes of Health/National Cancer Institute.