Cancer related pain is one of the most common symptoms experienced by cancer patients. A pain is called cancer pain when it is caused by the disease itself or due to any other factors directly associated with the disease or its treatment.
According to an estimate, about 59% of patients undergoing cancer treatment, about 64% of patients with advanced cancers, and about 33% of the patients after curative treatment report pain.
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The likelihood that a patient will have cancer related pain depends on many factors, like
- severity of disease (e.g., advanced disease is more likely to cause pain);
- type of disease (e.g., cancer affecting body parts with rich innervation or nervous system itself usually cause pain);
- type of treatment (e.g., surgery and radiotherapy are more likely to cause pain);
- age of patient (younger patients are more likely to have cancer pain).
Pain remains an under-reported symptom in cancer patients due to following misconceptions observed in people:
- Fear of taking too many medicines
- Fear of becoming addicted to pain medicines
- Too much side effects from pain relief medicines
- Not giving importance to report pain and consider it a normal part of having cancer.
Cancer pain can vary in intensity, duration, pattern, and response to treatment. Based on such characteristics, cancer pain can be divided into the following types:
An acute pain is short-lived intense pain that is usually caused by an injury or abrupt tissue damage. The pain subsides as the cause of injury is removed or injury heals.
A chronic pain is usually less intense than acute pain but last longer and is usually caused by some on-going tissue damage or a persistent problem. Continuous medication for a long duration is generally required for managing chronic pain.
A flare-up of chronic pain in patients who are already taking regular pain medicine is called a breakthrough pain. It may last for an hour or longer and usually does not respond to a regular dose of pain medicine. Sometimes it occurs during a particular activity, such as walking or dressing or it may occur unexpectedly.
This type of pain is usually experienced by a cancer patient a long time after surgery that involved removal of major body part, for example, a limb or a breast for the treatment of cancer. It is also sometimes referred to as post-amputation phenomenon. The phantom pain may last long and may not respond to general pain medicines.
What causes pain in cancer patients?
Pain in cancer patients can occur due to:
The most common cause of cancer pain is the disease itself. Most cancer cells grow and multiply indefinitely to form a tumor that can press on a nerve or spinal cord; destroy a bone or other organs; obstruct a passage for food, blood, or other body fluids; or disturb the function of a certain body part. All these can cause pain that usually lasts until the problem is cured by an appropriate treatment.
Most cancer patients have to undergo a range of diagnostic procedures to adequately assess disease severity. The diagnostic procedures can be painful with the pain caused by them ranging from a short-lived pain to a long-lived pain and from a dull pain to an intense pain.
Cancer treatment and the side effects associated with them can also lead to a variety of pain in cancer patients. Surgery usually involves removal of some body tissue and almost always associated with pain that may last from a few days to a few months, depending upon the extent of surgery.
Similarly, other cancer treatments usually involve the destruction of body tissue/cells and cause pain depending upon the magnitude of treatment. Additionally, the cancer treatment modalities usually have a range of side effects, like muscle spasms, constipation, mouth sores, skin rashes, hand and foot syndrome, nerve damage, and others. These side effects may also lead to pain or increase the severity of already existing pain.
Apart from the causes of cancer pain discussed above, cancer patients may have other coexisting medical problems that may cause additional discomfort ranging from physical to mental distress. This distress although unrelated to cancer may increase the severity of cancer pain.
How is the level of pain assessed in cancer patients?
Cancer related pain is a subjective feeling experienced by the patient, which is multidimensional in its implications. Patients usually have different pain thresholds and respond differently to the same dose of the same medicine. Thus, pain assessment should not be limited to the assessment of pain intensity. To be more meaningful, it should also include the assessment of the impact that pain has on patient’s quality of life.
Thus, various tools have been developed to assess the pain experienced by cancer patients. These tools involve asking single (simple tool) or multiple (complex tools) questions from the patient to evaluate the severity of pain that the patient has.
Visual Analog Scale
An example of a simple tool is a numerical rating scale (NRS) or a visual analog scale (VAS) wherein patient conveys the severity of pain on a scale from 0 to 10. The pain is considered mild, moderate, or severe if the response is 1 to 3, 4 to 6, or 7 to 10, respectively.
Various multifactorial tools encompassing a number of questions have been developed that help in assessing the impact of pain on a number of factors associated with the patient’s quality of life. Examples of such tools include:
- Brief Pain Inventory (BPI),
- McGill Pain Questionnaire,
- Memorial Pain Assessment Card, and others.
These tools are considered clinically meaningful in assessing the patient’s pain and are generally employed in clinical practice.
As a part of assessing the impact of pain via validated tools described above or separately, the treating physician would like to know the answers of following questions in order to prescribe an appropriate medicine to the patient:
- When did the pain first start?
- How long does the pain last and how frequent you feel the pain?
- Where is the pain hurts most?
- What is the intensity of pain (mild, moderate, or severe)?
- How does it feel? Is it sharp, dull, throbbing, cramping, steady, burning, pressing, etc.?
- Is there any pattern of time or location of pain occurrence (Is the pain worse during certain times of the day and always feel in a particular body part)?
- What makes you feel better or worse?
- Do you have any other problem due to pain, like trouble sleeping, fatigue, depression, or anxiety?
- Does pain affect your daily activities, such as eating, bathing, or moving around?
- Have you taken any medication or other intervention for pain relief?
- How effective are the current medication that you are using for pain relief?
- Is there any breakthrough pain (intense pain that flares up quickly even when pain control medicine is being used)?
The answers provided by the patient will be used by the treating physician to decide what type of treatment will work best for the patient. The doctor will continue assessing the level of pain during treatment and will change the type or intensity of treatment as per the patient’s requirements.
Different individuals respond differently to the same dose of the same drug. This is why each patient requires a personalized treatment plan for cancer pain.
Paracetamol (acetaminophen) and other nonsteroidal anti-inflammatory drugs (NSAIDs)
These are usually prescribed for patients with mild to moderate pain. They are generally very effective with fewer side effects if taken under medical supervision.
They are generally prescribed for patients with moderate to severe pain. Common side effects of opioids include constipation, nausea, vomiting, dry mouth, low blood pressure, dizziness, trouble thinking clearly, trouble sleeping, psychological problems or hallucinations, hot flashes, depression, etc.
Other drugs such as antidepressants, anticonvulsants, local anesthetics, corticosteroids, CNS stimulants, bisphosphonates, or denosumab may also be employed with or without above-discussed medicines in some patients. They help in improving other aspects of quality of life that have been impacted by pain and thus help in relieving pain indirectly.
Most patients can get adequate pain relief with pain medicines; However, some patients do not respond or develop side effects with analgesics. Some other treatment strategies can be employed for these patients, which may include:
Sometimes, a device is surgically implanted to deliver drugs or to stimulate nerves in a specific body part to control severe pain.
In other patients with unmanageable severe pain, surgery may be utilized to cut the nerves carrying the pain impulses to the brain. This procedure is also known as cordotomy since it involves cutting nerves near the spinal cord. Patient may get instant pain relief but it can cause irreversible loss of sensation in a particular body part, therefore, such procedures are employed only after careful risk-benefit analysis.
In this procedure, nerve carrying the pain impulses from the involved body part is blocked by injecting either a local anesthetic or some other drug around the nerve (or near its junction with spinal cord). The nerve blocks help to control severe and intense pain that can’t be controlled by other means. The duration of pain relief depends upon the drug used for nerve block.
Patients who have intense pain from the skin lesions, tumors pressing on some nerves, tumors causing blockage of some natural passage, or cancer cells that have spread to the bone may be treated with radiotherapy for controlling pain. The radiotherapy employed for relieving pain is known as palliative radiotherapy. The intent of such radiotherapy is management of pain to improve the quality of life of the patient.
Physiotherapy or light exercise and restricted synchronous body movements may be useful to relieve pain in patients with muscle weakness, wasting, or spasm. It also helps in stretching weak muscles, loosening stiff joints, maintaining coordination and balance, and regaining lost muscle strength.
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