Introduction

Although pain isn't always a prominent feature of cancer, it's one of the most feared symptoms. Nowadays there's no reason that most patients with cancer pain cannot be made comfortable. Apart from pills, there are many different ways of tackling the problem, so that pain shouldn't be the major concern of the patient with cancer. However, this sort of assurance requires an efficient cancer management team and attentive caregivers.

The first step in managing cancer pain is proper evaluation, and the review summarized here outlines the principles involved.

Assessment of cancer pain

There are various types of pain in cancer - that due to injury of tissues around the tumor (called nociceptive pain), the tumor's stimulation of nerves (called neuropathic pain), and individual mental responses to sensation from the tumor (psychogenic pain). Not surprisingly, self-reporting by the patient is the most important way to assess the pain.

A full history, physical exam, and appropriate lab and imaging studies (X-ray, CT, MRI) should reveal how the disease process is producing pain. But the time- course, its intensity, its features, and what makes it better or worse are all important in helping decide the best strategy for treatment.

Acute pain

The procedures ordered by the physician can sometimes produce acute pain: lumbar puncture (spinal tap), bone marrow biopsy, pleural tap, chemotherapy (especially by injection), hormone treatment (e.g. breast enlargement in men), immunotherapy (pain in the joints or muscles), and radiation (inflammation of the mucous membranes in the mouth or rectum). Such attacks can usually be managed with adequate doses of non-morphine analgesics.

Sometimes acute pain breaks through in patients with well-controlled chronic pain - treating this is discussed below.

Chronic pain

The most common cancer pain is due to bone pain. It is not known why some bone metastases are painless, and others are painful. If the spine is involved, there may be damage to the spinal cord or nerve roots. Other chronic pain conditions are due to neuropathic pain (e.g. post-mastectomy pain due to surgical damage to a nerve) or following radiation (fibrosis involving a nerve). Chemotherapy can sometimes cause persistent neuropathic pain, which stops when the chemo is discontinued.

Associated factors

Suffering by cancer patients is not limited to the awareness of pain. Additional problems - e.g. fatigue, misery, and social difficulties - must also be considered when managing pain. A team of different health professionals is best able to cover all the aspects involving the patient's quality of life, not just physical and psychological well-being, but also household, social, spiritual, and financial matters. Hospice programs are particularly suitable in this regard.

Drug treatment - the opioids

The mainstays of pain relief in cancer remain the derivatives of morphine, called opioid derivatives. One of the best guidelines for selecting the drug, route of administration, dose, frequency of dosing, and so on, is the 'analgesic ladder' recommended by the World Health Organization (WHO).

The choice of drug will depend on age, the presence of liver or kidney disease, possible interactions with other medications, etc. The oral route is usually preferred, but other routes (for instance, the transdermal skin patch) can be used if there is difficulty in swallowing or any severe gastrointestinal upset.

For continuous or frequently recurring pain, it's usually best to have a fixed schedule for dosing - e.g. every 4 hours - rather than giving the drug 'as needed'. Starting low, dosing is increased until pain relief is achieved or side effects prevent such an increase. If pain 'breaks through' the schedule, a 'rescue' dose can be added immediately; rescue dose levels are typically 5 -15% of the total daily dose of the drug

Oral doses can be given more often, if necessary, with as little as 1½ - 2 hours between doses; the minimum interval between intravenous (IV) administration can be as short as 10 - 15 minutes. It's important for everyone to know that there's no 'correct' dose or 'maximum' dose for cancer patients; the correct dose is simply 'enough'.

Development of side effects does not prevent further increase in doses; the treating physician can prescribe medications or other therapies to counteract the most common problems seen with opioids - nausea, vomiting, and constipation.

Non-opioid analgesics

Acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs, such as ibuprophen) are good painkillers, but they have a 'ceiling dose level' above which no more benefit can be expected. They are most useful in people with bone pain, or inflammatory pain, where the affected area is warm, red, and swollen. The newer COX-2 inhibitors may be superior types of NSAIDs in avoiding possible gastric or kidney toxicity.

Some drugs that are not primarily painkillers may have pain-relieving activity as well as their main effect. For instance, steroids, antidepressants, some anesthetics, anti-epilepsy drugs, and major tranquilizers may each be helpful in various cases of neuropathic pain. They are usually given after opioid therapy has been stabilized. In addition, certain types of cancer may do well with a particular drug directed at the tissue involved - e.g. bisphosphonates (such as Fosamax) or calcitonin for bone pain.

Radiation and chemotherapy

In addition to its main use (destruction of cancer cells), radiotherapy is often used for pain control, chiefly in managing bone metastases from lung, breast or prostate cancers; the response is usually good (70% to 80% of patients). Chemotherapy can provide pain relief in pancreas and prostate cancer due to tumor shrinkage; but there's often the problem of balancing this sort of improvement against the toxic effects that chemotherapy can produce.

Non-drug therapy

There are plenty of alternative treatments for cancer patients whose pain is not adequately controlled by medication. These are mostly done by specialists in hospital settings. The commonest ones are:

• Epidural opioid injections
• Continuous spinal local anesthesia
• Nerve blocks
• Acupuncture
• Exercise, heat or cold treatment
• Relaxation classes, hypnosis
• Individual, group, or family psychological therapy

A cancer treatment center or pain clinic is probably the best place for getting information and advice on these therapeutic approaches, if the patient's cancer management team does not offer them.

Alternative Medicine

Alternative (or Complementary) Medicine is becoming increasingly popular in the search for cancer pain relief, but few well-controlled studies have been done showing that such methods are truly effective. Physicians are likely to be open to a trial of such treatments, and be supportive if patients select one that is considered to be safe.