The Facts

People with cancer often feel severe or constant pain. The pain they experience depends on the type of cancer they have, the stage the disease is at, and the therapy they receive.

Although doctors agree that controlling cancer pain is a high priority, the pain isn't always understood or treated properly. This is often because of unfounded fears about people becoming addicted to painkillers.

Medicine has the tools to control cancer pain; in almost 90% of people, pain can be controlled very effectively. Pain control is extremely important, not only for people suffering from advanced cancer, but also for those whose condition may remain stable for years to come.

Causes

Pain can be defined as a complex sensation that reflects both damage to the body and the body's response to the damage. Physical pain has two sources. Nociceptive pain refers to pain relayed by nerves with the job of conveying damage in a part of the body. The pain is usually felt as aching or pressure; most cancer pain feels like this. But there's also the sharp, shooting, stabbing sensations of neuropathic (nerve) pain, which is caused by damage inside the nervous system. Experience of pain often combines different types of pain. Pain can also be made worse by the fear of getting sicker or of the pain itself.

People can experience intense, short-term acute pain or long-term chronic pain from cancer. The pain may be part of a cancer pain syndrome, a specific group of related pains. Cancer pain syndromes can be caused by tumours that:

• invade soft tissue or bone
• squeeze or infiltrate nerves or blood vessels
• obstruct a hollow organ like the intestines

Pain syndromes may also occur as a result of substances (hormones, proteins) produced by cancers that affect the function of other tissues and organs. Cancer pain syndromes may also follow surgery, radiation therapy, or chemotherapy. Identifying the cause of the pain is essential because knowing the cause makes managing the pain easier. Regardless of whether the cause is known or not, pain should always be adequately treated.

The assessment of pain is an ongoing process requiring constant attention to new pain. New pain or changes in pain patterns may signal treatable, minor problems. But changing pain is often a sign of growing disease. Because pain management relies on the treatment of the disease causing the pain, finding the reasons for any new pain is extremely important.

Symptoms and Complications

The type of pain someone may be in says a lot about their cancer. Pain and changes in pain can precede other signs of disease or complications by months. In these situations, a doctor's awareness of the kinds of pain a person feels may even save the person's life. The way someone feels a pain might be the only tip-off to a potentially life-threatening condition. For this reason, it's important to communicate changes in how you feel to your physician.

Cancer pain involves many complex relationships between complicating factors. It often involves pain caused by other problems that are indirectly started or made worse by the spread of cancer. For example, shingles, a painful skin infection, is far more common in people with cancer, possibly because of damage to their immune systems. But immune system problems may be further complicated by side effects from cancer treatments that also contribute to cancer pain. Radiation therapy and chemotherapy may significantly harm tissue and nerves; surgery can damage nerves. Many people with cancer take pain relievers just to offset these problems, which may continue after a cancer is treated.

The psychological effects of cancer pain can be devastating. Pain makes suffering worse by increasing feelings of helplessness, anxiety, depression, and despair. Whatever the status of the cancer, uncontrolled pain may prevent someone from working productively, enjoying recreation, or taking pleasure in family and society.

Cancer pain affects quality of life in four main ways:

• physically (people feel weak)
• psychologically (people feel unable to cope)
• socially (people's relationships suffer)
• spiritually (suffering may make people question their beliefs)

Making the Diagnosis

When a person sees their doctor to report pain, the focus will be on identifying its cause and developing a pain management plan. A physical exam and medical tests are required to help determine the origin of the pain. The description of the pain is very important to a doctor's understanding of its intensity and character. The patient may be given ways to explain or rate the pain, such as a questionnaire or an imagined pain intensity scale. The doctor may ask the patient how they cope with stress and pain, and inquire about their lifestyle.

Treatment and Prevention

Pain control is always essential. Unrelieved pain causes unnecessary suffering and weakens someone with cancer further. Whenever possible, pain is best relieved by treating the cancer. Pain may decrease when a tumour is removed by surgery or shrunk by radiation. However, other pain relief treatments are generally needed. Most doctors will ask people to use painkillers on a regular basis and not on an "as needed" basis. This avoids causing people anxiety from delaying the start of pain relief and ensures consistent pain relief with fewer fluctuations in pain control.

When the pain is mild to moderate, pain relievers like acetylsalicylic acid (ASA) or acetaminophen may work well. Nonsteroidal anti-inflammatory drugs (NSAIDS) like ibuprofen are effective on bone pain.*

If pain is severe, an opioid analgesic (strong painkillers from the drug family that includes morphine and codeine) may be prescribed. People will often continue to use ASA and acetaminophen in addition to opioid analgesics. Longer-acting opioids are often prescribed because they provide more hours of relief. Faster-acting opioid analgesics are used for pain that may break through the relief provided by longer-acting opioids.

Whenever possible, opioids are taken by mouth. However, some people are prescribed skin patches that deliver opioid analgesics through the skin. Others are given injections or use a continuous-infusion pump, connected to a catheter placed in a vein or under the skin. Some infusion pump systems allow the patient to control the release of the drug by pressing a button.

Opioid analgesics do have some side effects such as nausea, itchiness, drowsiness, and constipation. If these side effects are bothersome, they can be managed, sometimes with other medications. Nausea and drowsiness will usually decrease as treatment continues. However, most people require medications to help with constipation.

Over time, some people need bigger doses of opioids to control pain because the pain has gotten worse or they've developed drug tolerance. However, there is no maximum dose of opioid medications for treating cancer pain. If tolerance develops, the opioid dose can be increased.

When opioids are used to treat cancer pain, people do not get addicted. Addiction is defined as compulsive use in a person who craves the drug and uses it despite known potential consequences. People do become physically dependent and may experience withdrawal symptoms if the opioid is suddenly stopped, but they will not crave the medication. If the cancer is cured, most people stop using the opioid without serious difficulty. If the cancer can't be cured, being free of pain is essential.

Other mediations may also be helpful, especially for neuropathic (nerve) pain. These may include antidepressants, anticonvulsants, and muscle relaxants.

*All medications have both common (generic) and brand names. The brand name is what a specific manufacturer calls the product (e.g., Tylenol^®). The common name is the medical name for the medication (e.g., acetaminophen). A medication may have many brand names, but only one common name. This article lists medications by their common names. For more information on brand names, speak with your doctor or pharmacist.