Epidemiology of cancer pain and factors influencing poor pain control.

Pain is one of the most commonly experienced and feared symptoms of advanced cancer. Most cancer patients experience pain, usually of moderate to severe intensity, and most also have a number of distinct pains. The most common type of pain is related to bone metastases. Neuropathic pain occurs in one-third of patients, alone, or as a mix of nociceptive and neuropathic pain. The failure to manage pain properly is due to several factors. In developing countries, it is likely to be related to geography and limited resources. Legal restrictions also present barriers. In developed countries, failure to manage pain properly is usually related to a "disease" rather than a "symptom" model of care, which minimizes symptom management. Other factors include lack of physician education and failure to follow existing guidelines. Patients fear addiction, drug tolerance, and side effects. Despite adequate resources, pain is still undertreated.