Problems in Cancer Pain: Radiation Neuritis

By | September 26, 2011

Radiation therapy can be extremely effective for the treatment of prostate cancer, but the lumbar plexus is nearby and improperly designed portals and excessive doses can cause severe neuopathic pain.

Radiation neuritis come in two distinct varieties, the acute reaction which occurs during treatment and may improve after the completion of therapy and the chronic form which develops insidiously after a period of months to years. This distinction is important because presentation, clinical course and treatment differ greatly between the two.

Acute radiation neuritis can be thought of as deep, intense sunburn. It is a primary effect of the radiation, but as in other types of burns, either thermal or actinic, if the insult is small enough, the burn may heal with only minor sequelae. A common example of this is the recurrence of sciatica in prostate cancer patients receiving radiation treatments. If the pain can be treated symptomatically with physical therapy, traction or steroid injection, neurosurgical decompression can often be avoided. On the other hand if the insult is severe enough as in the case of third degree burns, the tissue is destroyed and no healing will occur, leaving the patient with severe neuropathic pain in the distribution of the nerves, which have been destroyed.

Chronic radiation neuropathy usually presents 3 to 5 years after the completion of radiation treatment. The progression of the disease is slow, but relentless. Nerves are fragile tissues, which lack the ability to regenerate themselves in most cases and with limited mechanisms for repair. Once sufficiently damaged, vital processes of cell metabolism, internal transport and control begin to fail and nerve cells begin to die prematurely in a piecemeal distribution. The result is a diffuse neuropathic injury and chronic pain.

Narcotics have no role in the treatment of either acute or chromic radiation neuritis. Antidepressants or antiepileptic agents may suffice in mild cases. Transcutaneous electrical nerve stimulation (TENS) may be helpful in mild to moderate cases where the nerves involved are superficial. When the involved nerves are deeper spinal cord stimulation may be effective, but in severe cases an intrathecal pain pump may be necessary. These are difficult cases, which require careful placement of the catheter near the site of injury and then the infusion of high doses of exotic mixtures. Pain can often be ameliorated if not completely relieved, but often at the expense of some impairment in motor function.

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