Key Terms: Acute, Chemotherapy, Chronic, CNS or central nervous system, Hepatic capsule, Iatrogenic, Metastasis, Neuropathy, Neurotransmitter, Nociceptor, Non-pharmacological, Palliative, Pharmacological, PNS or peripheral nervous system, Radiation, Stimulus.

Definition

Pain management in cancer care encompasses all the actions taken to keep people with cancer as free of pain as possible. It includes pharmacological, psychological, and spiritual approaches to prevent, reduce, or stop pain sensations.

Purpose

It is estimated that more than 800,000 new cases of cancer are diagnosed each year in the United States, and 430,000 cancer victims will die. Though recent figures are hopeful and suggest a decline in both the incidence of cancer and the number of people who die from it, studies have consistently shown that at least 70% of cancer patients in the advanced stage of the disease will experience significant pain. Pain is a localized sensation ranging from mild discomfort to an unbearable, excruciating experience. It is, in its origins, a protective mechanism, designed to alert the brain to injury or disease conditions. Unfortunately, when the cause of the pain is known, such as in diagnosed cancer, and treatment is initiated, pain can often continue.

Once the message of cancer has been received and interpreted by the brain, further pain can be counter-productive. Pain can have a negative impact on a person's quality of life, causing depression and impeding recovery. Unrelieved pain can become a syndrome in its own right and cause a downward spiral in a person's health and outlook. Proper pain management facilitates recovery, prevents additional health complications, and improves an individual's quality of life.

Several independent studies of the relief of pain have shown that pain is often under-treated by the medical profession. For this reason, in the spring and summer of 2000, the Joint Commission on Accreditation of Healthcare Organizations (JCAHO) and the American Pain Society (APS) developed standards for proper pain management.

Description

What Is Pain?

The treatment of pain has been a major endeavor since ancient times. By 400 B.C., the father of modern medicine, Hippocrates, had theorized that the brain, not the heart, was the controlling center of the body, and Greek anatomists had begun to identify various nerves and their purposes. The pain-relieving properties of opium were already known and were being utilized to stop suffering. Two thousand years ago, in China, acupuncture was being used to reduce pain.

Pain is the means by which the peripheral nervous system (PNS) warns the central nervous system (CNS) of injury or potential injury to the body. The CNS comprises the brain and spinal cord, and the PNS is composed of the nerves that stem from and lead into the CNS. PNS includes all nerves throughout the body except the brain and spinal cord.

A pain message is transmitted to the CNS by special PNS nerve cells called nociceptors. Nociceptors are distributed throughout the body and respond to different stimuli depending on their location. For example, nociceptors that extend from the skin are stimulated by sensations such as pressure, temperature, and chemical changes.

When a nociceptor is stimulated, neurotransmitters are released from cells. Neurotransmitters are chemicals found within the nervous system that facilitate nerve cell communication. The nociceptor transmits its signal to nerve cells within the spinal cord, which conveys the pain message to the thalamus, a specific region in the brain.

Once the brain has received and processed the pain message and coordinated an appropriate response, pain has served its purpose. The body uses natural pain killers, called endorphins, that are meant to derail further pain messages from the same source. However, these natural pain killers may not adequately dampen a continuing pain message. Also, depending on how the brain has processed the pain information, certain hormones, such as prostaglandins, may be released. These hormones enhance the pain message and play a role in immune system responses to injury, such as inflammation. Certain neurotransmitters, especially substance P and calcitonin gene-related peptide, actively enhance the pain message at the injury site and within the spinal cord.

It has been hypothesized that uninterrupted and unrelenting pain can induce changes in the spinal cord. In the past, intractable pain (pain that can't be managed or cured) has been treated by severing a nerve's connection to the CNS. However, the lack of any sensory information being relayed by that nerve can cause pain transmission in the spinal cord to go into overdrive, as evidenced by the phantom limb pain experienced by amputees. Evidence is accumulating that unrelenting pain or the complete lack of nerve signals increases the number of pain receptors in the spinal cord. Nerve cells in the spinal cord may also begin secreting pain-amplifying neurotransmitters independent of actual pain signals from the body. Immune chemicals, primarily cytokines, may play a prominent role in such changes.

What Is Cancer Pain?

The majority of cancer pain results from a cancerous tumor pressing on organs, nerves, or bone. However, several studies by pain-pioneer Dr. John Bonica and others have shown that a predictable 78% of all cancer pain is indeed related to the disease, but an impressive 19% was found to be caused instead by treatment of the cancer. Three percent of all complaints of pain were unrelated to either the disease or treatment.

Cancer pain is generally divided into three categories:

• Visceral pain, usually caused by pressure resulting from the invasiveness of the tumor, expansion of the hepatic capsule, or injury caused by radiation or chemotherapy.
• Somatic pain often resulting from bone metastasis.
• Neuropathic pain, or pain caused by the pressure of a tumor on nerves, or the trauma to nerves resulting from either radiation, chemotherapy, or surgery.

Managing Cancer Pain

Pharmacological Options

General guidelines developed by the World Health Organization (WHO) for pain management apply to cancer pain management as well. These guidelines follow a three-step ladder approach:

• Mild pain is alleviated with acetominophen or nonsteroidal anti-inflammatory drugs (NSAIDs). NSAIDs and acetaminophen are available as over-the-counter and prescription medications, and are frequently the initial pharmacological treatment for pain. These drugs can also be used as adjuncts to the other drug therapies, which might require a doctor's prescription. NSAIDs include aspirin, ibuprofen (Motrin, Advil, Nuprin), naproxen sodium (Aleve), and ketoprofen (Orudis KT). These drugs are used to treat pain from inflammation and work by blocking production of pain-enhancing neurotransmitters, such as prostaglandins. Acetaminophen is also effective against pain, but its ability to reduce inflammation is limited. NSAIDs and acetaminophen are effective for most forms of acute (sharp, but of a short course) pain.
• Mild to moderate pain is eased with a milder opioid medication plus acetominophen or NSAIDs. Opioids are both actual opiate drugs such as morphine and codeine, and synthetic drugs based on the structure of opium. This drug class includes drugs such as oxycodone, methadone, and meperidine (Demerol). They provide pain relief by binding to specific opioid receptors in the brain and spinal cord, and thus block the perception of pain.
• Moderate to severe pain is treated with stronger opioid drugs plus acetominophen or NSAIDs. Morphine is sometimes referred to as the "Gold Standard" of palliative care as it is not expensive, can be given starting with smaller doses and gradually increased, and is highly effective over a long period of time. It can also be administered orally (by mouth), rectally, or by injection. A newer method of administering morphine involves a patient-controlled delivery system implanted in the covering of the spinal cord. Researchers in North Carolina reported in late 2003 that the new system not only provided more effective pain relief, but also lowered the patients' use of morphine and the complications associated with long-term use of morphine. In general, the development of implantable pumps has greatly improved pharmacological approaches to pain management.

Although antidepressant drugs were developed to treat depression, they are also effective in combating chronic headaches, cancer pain, and pain associated with nerve damage. Antidepressants shown to have analgesic (pain reducing) properties include amitriptyline (Ela vil), trazodone (Desyrel), and imipramine (Tofranil). Anticonvulsant drugs share a similar background with antidepressants. Developed to treat epilepsy, anticonvulsants were found to relieve pain as well. Drugs such as phenytoin (Dilantin) and carbamazepine (Tegretol) are prescribed to treat the pain associated with nerve damage.

Close monitoring of the effects of pain medications is required in order to assure that adequate amounts of medication are given to produce the desired pain relief. When a person is comfortable with a certain dosage of medication, oncologists typically convert to a long-acting version of that medication. Transdermal fentanyl patches (Duragesic) are a common example of an long-acting opioid drug often used for cancer pain management. A patch containing the drug is applied to the skin where the drug is continuously absorbed by the body, usually for three days. Pumps are also available that provide an opioid medication upon demand when the person is experiencing pain. By pressing a button, they can release a set dose of medication into an intravenous solution or an implanted catheter. Another mode of administration involves implanted catheters that deliver pain medication directly to the spinal cord. Delivering drugs in this way can reduce side effects and increase the effectiveness of the drug. Research is underway to develop toxic substances that act selectively on nerve cells that carry pain messages to the brain, killing these selected cells, and thus stopping transmission of the pain message.

Non-Pharmacological Options

Pain treatment options that do not involve drugs are often used as adjuncts to, rather than replacements for, drug therapy. One of the benefits of non-drug therapies is that an individual can take a more active stance against pain. Relaxation techniques, such as yoga and meditation, are used to shift the focus of the brain away from the pain, decrease muscle tension, and reduce stress. Tension and stress can also be reduced through biofeedback, in which an individual consciously attempts to modify skin temperature, muscle tension, blood pressure, and heart rate. A group of researchers in New York reported in 2003 that the hypnotic-like approaches—particularly imagery, relaxation techniques, and hypnotic suggestion—appear to be more effective in managing pain than other behavioral approaches.

Participating in normal activities and exercising can also help control pain levels. Through physical therapy, an individual learns beneficial exercises for reducing stress, strengthening muscles, and staying fit. Regular exercise has been linked to production of endorphins, the body's natural pain killers.

Acupuncture involves the insertion of small needles into the skin at key points. The acupuncturist will usually stimulate points on the ear when treating cancer pain. Acupressure uses these same key points, but involves applying pressure rather than inserting needles. Both of these methods may work by prompting the body to release endorphins. Applying heat or being massaged are very relaxing and help reduce stress. Transcutaneous electrical nerve stimulation (TENS) applies a small electric current to certain parts of nerves, potentially interrupting pain signals and inducing release of endorphins. To be effective, use of TENS should be medically supervised.

A new method for managing pain in children with cancer is virtual reality, which works by distracting the child's attention from the pain and accompanying anxiety. Virtual reality has been used successfully in the treatment of anxiety disorders, and shows great promise in treating children suffering from cancer pain. Larger-scale studies are under way as of late 2003.

Preparation

Assessment of cancer pain is absolutely essential to good pain management. Pain scales or questionnaires are sometimes used to attach an objective measure to a subjective experience. Objective measurements allow health care workers a better understanding of the pain being suffered by the patient. Pain has been called "the fifth vital sign," (temperature, pulse, respiration and blood pressure being the other four vital signs), by the Veterans Administration. Evaluation also includes physical examinations and diagnostic tests to determine underlying cause of the pain. Some evaluations require assessments from several viewpoints, including neurology, psychiatry and psychology, and physical therapy.

Risks

Owing to toxicity over the long term, even non-prescription drugs must be carefully monitored in chronic pain management. NSAIDs have the well-known side effect of causing gastrointestinal bleeding, and long-term use of acetaminophen has been linked to kidney and liver damage. Other drugs, especially narcotics, have side effects such as constipation, drowsiness, and nausea. Sedation can often be reduced by the timing of when medication is taken (such as at bedtime), and constipation can be reduced by increasing the amount of fruits, vegetables, and whole-grain foods in the diet, or by the use of laxatives, stool softeners, or even enemas. Serious side effects can also accompany antidepressants and anticonvulsants, which may discourage or prevent their use depending upon the circumstances. These side effects include mood swings, confusion, bone thinning, cataract formation, increased blood pressure, and other problems.

Non-pharmacological therapies carry little or no risks. However, it is advised that individuals recovering from serious illness or injury consult with their health care providers or physical therapists before making use of adjunct therapies. Invasive procedures carry risks similar to other surgical procedures, such as infection, reaction to anesthesia, iatrogenic injury (injury as a result of treatment), and heart failure.

A traditional concern about narcotics use has been the risk of promoting addiction or tolerance. As narcotic use continues over time, as in terminal cancer, the body becomes accustomed to the drug and adjusts normal functions to accommodate to its presence. Therefore, to elicit the same level of action, it is necessary to increase dosage over time. Tolerance can be defined as a gradual lessening of the effectiveness of an opioid drug from continued use.

Many studies involving cancer patients have indicated that proper dosage of narcotic medication does not create an addiction to it. A major concern for many cancer patients though, is that the medication will stop working for them. Evidence suggests this is not true. A simple increase in the dose will usually cause the medication to relieve pain again. One of the biggest dangers is abruptly stopping an opioid medication or reducing the dose, as the person can then go into withdrawal, a potentially serious medical condition characterized by agitation, rapid heart rate, profuse sweating and sleeplessness.

However, physical dependence is different from psychological addiction. Physical dependence is characterized by discomfort if drug administration suddenly stops, while psychological addiction is characterized by an overpowering craving for the drug for reasons other than pain relief. Psychological addiction is a very real and necessary concern in some instances, but it should not interfere with a genuine need for narcotic pain relief.

Normal Results

Effective application of pain management techniques reduces or eliminates cancer pain. This treatment can improve an individual's quality of life and aid in recovery.

Questions to Ask the Doctor

• Does my type of cancer usually cause pain, and if so, how will the pain be treated?
• Does the radiation or chemotherapy that I may have cause pain?
• What are the side-effects of the medications you will order?
• What things can I do to help with my pain management?
• Does the pain necessarily mean that the cancer is getting worse?

Perhaps the best measure of the results of pain management for cancer patients would be the fulfillment of the recently developed Bill of Rights for Cancer Pain. It is as follows:

• You have the right to be believed about the severity of your pain.
• You have the right to have your pain controlled.
• You have the right to have pain resulting from treatments and procedures prevented, or at least minimized.
• You have the right to be treated with respect at all times when you need medication; to not be treated like a drug abuser.

Resources

Periodicals

Alimi, D., C. Rubino, E. Pichard-Leandri, et al. "Analgesic Effect of Auricular Acupuncture for Cancer Pain: A Randomized, Blinded, Controlled Trial." Journal of Clinical Oncology 21 (November 15, 2003): 4120–4126.

Gershon, J., E. Zimand, R. Lemos, et al. "Use of Virtual Reality as a Distractor for Painful Procedures in a Patient with Pediatric Cancer: A Case Study." Cyberpsychology and Behavior 6 (December 2003): 657–661.

Mundy, E. A., K. N. DuHamel, and G. H. Montgomery. "The Efficacy of Behavioral Interventions for Cancer Treatment-Related Side Effects." Seminars in Clinical Neuropsychiatry 8 (October 2003): 253–275.

Perron, Vincent, MD, and Ronald S. Schonwetter, MD. "Assessment and Management of Pain in Palliative Care Patients." Cancer Control: Journal of the Moffitt Cancer Center 27 (January 2001).

Rauck, R. L., D. Cherry, M. F. Boyer, et al. "Long-Term Intrathecal Opioid Therapy with a Patient-Activated, Implanted Delivery System for the Treatment of Refractory Cancer Pain." Journal of Pain 4 (October 2003): 441–447.

Rosenthal, K. "Implantable Pumps Deliver Innovative Pain Management." Nursing Management 34 (December 2003): 46–49.

Organizations

American Chronic Pain Association. PO Box 850, Rocklin, CA 95677-0850. (916) 632-0922. .

American Pain Society. 4700 West Lake Ave., Glenview, IL 60025. (847) 375-4715. .

Cancer Care, Inc. "Bill of Rights for Cancer Pain." .

National Cancer Institute. "Cancer Facts." [citedSeptember 26, 2000]. .

National Chronic Pain Outreach Association, Inc. PO Box 274, Millboro, VA 24460-9606. (540) 997-5004.

—Julia Barrett; Joan Schonbeck, R.N.; Rebecca J. Frey, Ph.D.

Gale Encyclopedia of Cancer. Copyright © 2006 by The Gale Group, Inc. All rights reserved.