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. Approximately 40% of people undergoing treatment for cancer experience pain at some point, though this percentage tends to increase depending on the severity and curability of the cancer.
Cancer pain can be defined as a complex sensation that reflects both damage to the body and the body's response to the damage. Although doctors agree that controlling cancer pain is a high priority, pain isn't always understood or treated properly. This is often because of unfounded fears about people with cancer becoming addicted to painkillers.
About 9 out of 10 people suffering from cancer pain find pain relief through medication therapy. 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.
Physical cancer pain has 2 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.
- Neuropathic (nerve) pain refers to pain caused by damage inside the nervous system. The pain is usually felt as sharp shooting and stabbing sensations.
Experience of pain is often a combination of different types of pain. Pain can also be made worse by the fear of pain itself or of getting sicker.
People can experience intense short-term acute pain or long-term chronic pain from cancer. The pain can also be part of a cancer pain syndrome. Cancer pain syndromes can be caused by tumours that:
- invade soft tissue or bone (including bone fractures)
- squeeze or infiltrate nerves or blood vessels
- obstruct a hollow organ like the intestines
- hemorrhage into a tumour
Cancer 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. If pain is not adequately treated in the short term, it can worsen and become more difficult to control later on.
The assessment of cancer pain is an ongoing process requiring constant attention to new pain. New pain or changes in pain patterns may signal minor problems that are treatable. But changing pain is often a sign of growing disease. Because cancer 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
Cancer pain can be described as dull aching, pressure, burning, or tingling. The type of pain often gives clues about the sources of the pain. For example, pain caused by damage to nerves is usually described as burning or tingling, whereas pain affecting internal organs is often described as a sensation of pressure.
The type of pain someone experiences also says a lot about their cancer. Pain and changes in pain can precede other signs of disease or complications a few months ahead. 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 doctor.
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 tissues and nerves, and surgery can damage nerves. Many people with cancer take pain relievers just to offset these problems, which may continue after the 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 their surroundings.
Cancer pain affects quality of life in 4 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 (e.g., is it dull, sharp, achy, or shooting). The patient may be given ways to explain or rate the pain, such as a questionnaire or a 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 further weakens someone with cancer. Whenever possible, pain is best relieved by treating the cancer. Pain may decrease when a tumour is removed by surgery or shrunk by radiation or chemotherapy. 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 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 medication family that includes morphine and codeine) may be prescribed. People will often continue to use acetaminophen in addition to opioid analgesics. Longer-acting opioids are often prescribed because they provide more hours of relief and are taken on a regular basis. Faster-acting opioid analgesics are taken on an as-needed basis and 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 as injections or through a continuous infusion pump that's 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 medication 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 tolerance to the medication. However, there is no maximum dose of opioid medications for treating cancer pain. If tolerance develops, the opioid dose can be increased. Cancer pain is often inadequately treated. Some reasons for this include reluctance of the patient to bring up the pain (perhaps for fear of "bothering" their doctor or that their condition is worsening), reluctance of the doctor to inquire about pain or prescribe opioids, and fear of addiction. Addiction can occur for people receiving opioids for cancer pain. When opioids are being considered, doctors should assess every patient for risk factors for addiction, and carefully prescribe based on their clinical judgement.
Other mediations may also be helpful, especially for neuropathic (nerve) pain. These may include antidepressants, anticonvulsants, and muscle relaxants. Nerve blocks, where a local anesthetic is injected onto or near nerves, may also be used. For severe cases of pain related to cancers of the bone, medications called bisphosphonates may also be prescribed.
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