What is cancer pain?

Cancer pain is a common complication of cancer diseases. Because of the chronic and progressive nature of the disease, cancer pain is a common cause of chronic pain. Cancer pain results from tissue damage – either due to the disease itself, or due to treatment (chemotherapy, radiotherapy). The principles of management of cancer pain include:

  • Treatment of the cancer
  • Providing information, counselling and support to the patient
  • Effective treatment of the pain
  • Setting realistic goals for pain management

Pain is a common symptom in patients with cancer, with one third experiencing pain at diagnosis and two thirds experiencing pain with advanced cancer. Treatment for cancer pain will vary between patients, as different patients may experience different levels of pain even if they have the same form of cancer.


Types of cancer pain

For effective treatment of pain, it is essential to first work out which type or types of pain are being experienced by the patient, so that treatment can be targeted appropriately. Some common types of pain experienced by cancer patients include:

  1. Pressure Pain This is related to either the size or the location of the expanding tumour – it may compress surrounding structures or cause blockages depending on where it is.
  2. Nociceptive pain The pain that results from the stimulation of sensory nerves in the tissues and bones. The “trademark” feature of this type of pain is that the patient can localise or “pin point” the pain usually with one finger. The first-line treatment for this type of pain is often aspirin. Opioids, corticosteroids or antidepressant medications are also sometimes used.
  3. Somatic pain Pain from nerve ending in tissues or bones which may feel ‘aching’ or ‘gnawing’. It commonly results from bone metastases, fractures, or large bruises.
  4. Neuropathic Pain Related to damage or irritation to nerves. It is often described as sharp, flashing, burning, like an electric shock or tingling. It is commonly experienced in gynaecological cancers, as well as cancers of the rectum or penis. It is difficult to treat, often requiring a combination of medications.

Other types of pain, including pain from muscle spasms and referred pain from internal organs, may also be experienced.

Refractory pain

Refractory pain means pain that continues or worsens despite attempts at treatment. It is not uncommon amongst cancer patients. Some risk factors for refractory pain include:

  • Neuropathic pain
  • Multiple pains and pain mechanisms
  • Long-standing pain or pain resistant to medication
  • Poor response to analgesics in the past
  • Adverse effects to analgesics
  • History of drug and alcohol dependency


Pain wind-up

With time, cancer pain can increase in some patients – either due to progression of the disease (with new sites involved), or due to a phenomenon called ‘pain wind-up’. Pain wind up is the phenomenon where patients require increasing doses of opioids (a type of pain-relieving medication) over a short period of time or have rapidly increasing pain scores over a short period of time (for example, from a pain score of 0 (no pain) to a score of 10 (worst pain ever felt)). Pain wind up is a type of opioid insensitive pain – opioids will not relieve pain wind up. The cause of pain wind up is usually inadequate treatment of pain or misdiagnosis of neuropathic pain. Pain wind up can usually be prevented by correct pain diagnosis and aggressive use of pain relieving medications together with clear precise explanations given to you, the patient.


Treatment of cancer pain

Cancer pain can be controlled in over 90% of cases, often with medications alone. Even when pain is not completely controlled, the patient has enough reduction in their pain to undertake most every-day activities. There are a large number of analgesics and adjuvant (additional) drugs that are used in cancer pain management.
In general, each cancer patient will be prescribed the following:

  • An analgesic or a combination of these to be taken on a regular basis.
  • An analgesic to be taken as needed for breakthrough pain, or pain that occurs between regular doses of the first analgesic.
  • A laxative such as coloxyl and senna if opioids are prescribed, as these often cause constipation.
  • Anti-nausea medications, especially if opioids are prescribed, as these often cause nausea and vomiting, but also as cancer treatments such as chemotherapy and radiotherapy can also cause nausea and vomiting.

Some examples of drugs used to treat cancer pain include:

  • Simple Analgesics: E.g. aspirin, paracetamol, non-steroidal anti-inflammatory drugs. These should be used for mild pain and in combination with other agents (opioids, adjuvants) for more severe pain.
  • Opioids: Opioid analgesia does not shorten the life of patients with cancer. Addiction and tolerance are also not significant with the use of opioids in patients with cancer. It is important that the pain is treated aggressively because pain not properly treated can have a significantly negative impact on your quality of life.
  • Adjuvant drugs: These may include local anaesthetics, antiarrhythmics, antiepileptics, corticosteroids, muscle relaxants, and even inhalational drugs like nitrous oxide.

Analgesic medication can be given in a number of different ways, including orally, as intravenous or intramuscular injections, as a suppository, or into epidural or intrathecal catheters. Pain relief can also be given as patient-controlled analgesia (PCA) where the patient has control over when the dose is given. The desired route and mode of administration should be tailored to the patient’s condition and preference.
Some types of cancer pain are particularly suited to a particular treatment. For example:

  • Nociceptive visceral pain: This type of pain typically responds well to opioids such as fentanyl (Durogesic). The dose of opioids is increased until the pain has completely gone, though care should be taken to avoid overdosing.
  • Nociceptive somatic pain: It is often not possible to completely control this pain by only using an opioid. Simple analgesics (e.g. paracetamol, NSAIDs) as well as adjuvants (e.g. dexamethasone) are often given as well.
  • Neuropathic pain: Requires a combination of medications. It is relatively opioid resistant so anti-epileptic and anti-depressant medication in combination with an opioid form is the principal role in management of this type of pain.
  • Pain wind-up: (See above) Also requires specific treatment.

Non-pharmacological treatments

Non-pharmacological treatments for cancer pain (ie. techniques that don’t rely on medication) are useful in the treatment of cancer pain, as they increase the success rate of treatment and lower pain scores. They may include:

  • Physical techniques: eg physiotherapy, muscle relaxation, nerve blocks, surgery;
  • Psychological treatment: behaviour modification, family therapy, hypnosis, psychotherapy, stress management, art and music therapy, distraction techniques;
  • Social factors: community support groups, occupational therapy, self-help groups.


Presentation by Dr Dean on cancer pain

Please click here to view a lecture given on cancer pain by Dr Andrew Dean, MB ChB MRCP(UK) FRACP, Medical Director of Virtual Medical Centre.

References

  1. Woodruff, R. Cancer Pain. 2nd Ed. 1999. Asperula Pty Ltd. Heidelberg.