Cancer pain

• What is Cancer Pain
• Statistics on Cancer Pain
• Risk Factors for Cancer Pain
• Progression of Cancer Pain
• Symptoms of Cancer Pain
• Clinical Examination of Cancer Pain
• How is Cancer Pain Diagnosed?
• Prognosis of Cancer Pain
• How is Cancer Pain Treated?
• Cancer Pain References

What is Cancer Pain

Cancer Pain is one of the complications 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). Before considering treatment of cancer pain, it should be noted that separate types of pain are described – the distinction is important as far as treatment is concerned.

1. Visceral pain
Visceral pain is pain which originates from the contents of the thorax (chest) or the abdomen (tummy). Visceral pain is usually very poorly localised. In its mildest form it is described as a ‘discomfort’ or a ‘pressure’. As the pain increases it may be described as ‘deep’ or ‘aching’.

2. Somatic pain
Somatic pain is defined as pain originating from the nerve endings. These include bone, skin, muscle, the pericardium (heart), the peritoneum (abdomen), the pleura (lungs). This also includes pain from the liver capsule. Somatic pain is usually very well localised.

3. Neuropathic pain
Neurogenic pain is defined as pain originating from damage/irritation to the nerve pathway. Neurogenic pain is usually described as sharp, shooting, burning, tingling, pins and needles or piercing. Neurogenic pain is usually severe and as it is relatively opioid resistant a combination of drugs is required.

Statistics on Cancer Pain

Cancer pain is feared amongst cancer patients and approximately two-thirds of patients experience significant cancer pain throughout the course of their disease. This is a significant number considering the vast amount of cancer cases worldwide every year.

Risk Factors for Cancer Pain

Pain in patients with cancer is often undertreated – and a number of factors may contribute to this. Sometimes the spiritual, social, and psychological distress of the patient contribute to the total experience of cacner pain. 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.

Progression of Cancer Pain

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 over a short period of time or have rapidly increasing cancer pain scores over a short period of time (pain score example: 0 = no pain, 10 = worst pain ever felt). Pain wind up is a type of opioid insensitive pain – opioids will not relieve pain wind up. The causes of pain wind up is usually inadequate treatment of cancer pain or misdiagnosis of neuropathic pain. Pain wind up can usually be prevented by correct cancer pain diagnosis and aggressive use of pain relieving medications together with clear precise explanations given to you, the patient.

How is Cancer Pain Diagnosed?

• Acute cancer pain: Investigations should be guided by the presentation itself (e.g. appropriate investigations for patients with abdominal pain/chest pain, etc);
• Chronic cancer pain: Detailed investigations are often harmful and should be limited to when they are likely to influence management.

Prognosis of Cancer Pain

The prognosis of the cancer itself will obviously vary and this is not discussed here. As far as the cancer pain is concerned, it can be controlled in over 90% of cases, often with medications alone. Even when cancer pain is not completely controlled, the patient has enough reduction in their pain to undertake most everyday activities.
Poorly controlled cancer pain and adverse effects of some pain medications such as opioids, can contribute to depression, suicidal thoughts or requests for aid in dying. It is also difficult and uncomfortable to witness for those trying to care for the dying patient.

How is Cancer Pain Treated?

As mentioned, the first step in cancer pain management is to identify the type of cacner pain present as the treatments vary. Treatments targetting the actual cancer such as chemotherapy, radiotherapy and surgery often help with the cancer pain. Other treatments are targetted at relieving symptoms. Patients are often started on milder drugs and progressively worked up to more stroger drugs such as morphine if the cancer pain doesn’t settle. Cancer pain is better controlled when patients, their families, carers, and clinicians work together to obtain the best pain management.
Currently, there are a large number of analgesics and adjuvant (additional) drugs that are used in cancer pain management.

1. Simple analgesics
Such as 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.

2. Opioids
Such as morphine, methadone, oxycodone and fentanyl are used in cancer patients. Often they may be used in conjunction with laxatives and anti-nausea agents to treat side-effects. Giving people opioid analgesics does not shorten life or cause addiction contrary to public belief. With cancer pain, it is important that the pain is treated aggressively because cancer pain not properly treated can have a significantly negative impact on your quality of life.

3. Adjuvant drugs
These are usually given in combination and include:

• Local anaesthetics (e.g. lignocaine, bupivacaine, ropivacaine);
• Antiarrhythmics for neuropathic pain (e.g. mexiletine, fleicanide);
• Antiepileptics (e.g. carbamazepine, gabapentin, sodium valproate);
• Tri-cyclic antidepressants (e.g. amitryptilline, desipramine, dothiepin, imipramine);
• Corticosteroids to reduce tissue oedema (e.g. brain tumours, liver metastases);
• Skeletal muscle relaxants (e.g. benzodiazepines such as clonazepam, diazepam and midazolam; baclofen);
• Inhalational agents (e.g. nitrous oxide, methoxyflurane).

Analgesic medication can be given in a number of routes depending on your specific circumstances and preference. As far as tailoring the medication to the specific type of cancer pain:

• Visceral pain: should respond well to opioids. The dose of opioids is increased until the pain has completely gone, though care should be taken to avoid overdosing;
• Somatic pain: It is often not possible to completely control this pain by only using an opioid (morphine group of drugs). Simple analgesics (e.g. paracetamol, NSAIDS) as well as adjuvants (e.g. Dexamethasone) are often given as well;
• Neurogenic pain: Requires a combination of medications. It is relatively opioid (morphine group of drugs) 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.

4. Non-pharmacological management
Should also be combined because it increases the success rate of the treatment. This may include:

• Physical techniques: 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.

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.

Cancer Pain References

1. Bajwa Z, Warfield C. ‘Overview of cancer pain.’ UpToDate, 2006.
2. Kumar and Clark. Clinical Medicine, 5th ed. WB Saunders, Toronto (2002).
3. Therepeutic guidelines. Analgesic 2003.
4. www.cancer-pain.org
5. www.virtualcancercentre.com