Colon Cancer Pain Still Undertreated

CHICAGO--Over the last decade, increasing attention has been paidto the palliative care of patients whose colon cancer has notresponded to curative treatment so that they may achieve the bestpossible quality of life.

For one aspect of palliative care--pain management--there is stillwidespread undertreatment, however, Richard Payne, MD, said atthe National Conference on Colorectal Cancer, sponsored by theAmerican Cancer Society. More than 1.3 million copies of clinicalpractice guidelines on pain management were distributed by theAgency for Health Care Policy and Research in 1994 (see box onpage 28). Yet, far too many cancer patients are still not achievingadequate pain relief.

A 1995 study from the University of Wisconsin that surveyed morethan 1,300 patients with advanced or metastatic cancer found that67% of patients had pain and took analgesics on a daily basis.

A third of these patients had pain severe enough to impair function,and 46% had negative pain management index scores, meaning theydid not receive an analgesic regimen in keeping with the severityof their pain, said Dr. Payne, associate professor of medicine,M.D. Anderson Cancer Center.

Of the survey patients with GI tumors, including colorectal, gastric,and pancreatic tumors, 61% reported pain primarily due to encroachmentof tumors on pain-sensitive structures or bowel obstruction; 58%classified their pain as 5 or worse on a 0 to 10 scale, and 41%had a negative pain management index.

A 1993 study of colon cancer patients showed that among thosewith moderate pain, activity was impaired in 47%, ability to walkin 32%, ability to work in 55%, ability to sleep in 55%, and moodand enjoyment of life in 55%. Yet, Dr. Payne said, use of thethree-step analgesic ladder can successfully manage pain in 75%to 90% of cancer patients.

The three-step analgesic ladder stratifies pain as mild, moderate,or severe, and assigns an analgesic regimen appropriate for thepain intensity. The regimen for mild pain includes nonopioid,nonsteroidal anti-inflammatory agents or tricyclic antidepressants,particularly for neuropathic pain. Moderate pain is managed withweak opioids, such as codeine, and severe pain is treated withopioids.

Physicians most often cite fear that patients will develop toleranceas the reason they restrict analgesic opiate dosing. However,the concept of tolerance is misunderstood, Dr. Payne said. "Tolerancein cancer patients is caused more by the progression of the diseaseand the increase in the pain stimulus rather than by a changein opiate receptivity or respon-sivity," he explained.

As a result, tolerance is incomplete. "If a patient is developinga dose-limiting toxicity at higher doses of morphine, one canswitch the patient to hydromor-phone or fentanyl, and still obtainanalgesia," he noted. Tolerance also varies with differentroutes of administration. If tolerance to intravenous opioidsoccurs, opioid analgesics may be given via the spinal route atlower doses.

Intractable Pelvic Pain

Patients with intractable pain in the pelvis and perineum, particularlypain in the midline or bilateral locations due to tumor infiltrationof pain-sensitive structures, may not achieve adequate relieffrom systemic opioids, he said. These patients may benefit fromspinal administration of both opioids and nonopioids.

"A dilute solution of a local anesthetic may be given ina dose that produces a sensory block without a motor block sopatients can still walk and function," Dr. Payne said. Drugssuch as clonidine, an alpha-2 agonist, also are effective whendelivered to the spinal cord.

Less than 2% of patients with intractable pelvic visceral paintreated at M.D. Anderson have undergone a midline myelotomy, duringwhich pain fibers in the spine are severed. Because the spinaltracts that control micturition and motor control are spared duringthe surgery, the risk of paralysis or loss of bladder controlis kept low, Dr. Payne said.

Myelotomy has been effective in 85% of these patients initially,but the pain relief response rate has fallen to 55% of patientsafter 1 year.

To Order Cancer Pain Guidelines

To order copies of the Agency for Health Care Policy and Research(AHCPR) publications--Clinical Practice Guidelines for the Managementof Cancer Pain and the Quick Reference Guide for Clinicians: Managementof Cancer Pain: Adults--call the Agency Clearinghouse at 1-800-358-9295.