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Key Words: implantable drug-delivery system, narcotics, pain management. (Definitions of many terms related to cancer can be found in the Cancer.gov Dictionary ⁴.)

Patients with advanced cancer who used an implantable drug-delivery device to control their pain had better pain relief, fewer toxic side effects, and better survival than patients who received intensive medical pain management, researchers reported in the October 1, 2002, issue of the Journal of Clinical Oncology (see the journal abstract).

The multicenter trial involved 202 patients who were randomly assigned to two groups. One group received comprehensive medical management (CMM) for their pain. CMM is a more systematic approach to pain control than cancer patients typically receive. It involves a team of health care professionals with special training in pain management who search for the most effective pain medication for each patient by starting with the least toxic and only gradually moving up to medications with more side effects until the pain is relieved. CMM may also include the use of complementary methods of pain reduction such as relaxation, guided imagery, psychotherapy, and patient support groups.

The trial's second group received CMM plus the implantable device. Implantable drug delivery systems (IDDSs) deliver narcotic pain medications directly to the spinal fluid, using much smaller doses than are required when the same drugs are taken by mouth or injected. The device consists of a small, battery-powered, programmable pump implanted under the skin of the abdomen and connected to a small catheter. Although IDDSs have been in use since 1991, this was the first randomized trial to compare the device with CMM for cancer pain.

Upon entering the study, most trial participants were taking at least 250 milligrams per day of narcotic pain relievers, such as morphine. Many were also taking additional medications such as antidepressants and anticonvulsants for pain relief.

During the study, patients in the CMM-only group continued to take morphine or similar narcotic drugs by mouth, plus additional medications as needed. Most IDDS patients received morphine via the pump; the others received hydromorphone (Dilaudid®), a drug used to treat pain. IDDS patients could take additional narcotics by mouth if necessary.

At study entry, all trial participants rated their pain as well as the side effects of their pain medication (such as sedation, clouded thinking, constipation, and fatigue) on scales from 0 (least) to 10 (worst). Both the CMM-only group and the CMM-plus-IDDS group had average pain scores of more than 7.5 at the start of the trial.

But four weeks later, pain scores for IDDS patients fell to an average of 3.7 (a 51.5 percent reduction). In CMM patients, average pain scores dropped to 4.8 (a 39 percent reduction). IDDS patients also experienced a 50 percent reduction in toxic side effects after four weeks. By contrast, in patients who received CMM alone, toxic side effects declined by 17 percent.

When the researchers looked to see how many individuals in each group lowered their pain and side-effects scores by 20 percent or more, they found that 58 percent of patients using the implantable device had achieved this level of relief compared with 38 percent of patients who received CMM alone.

Survival rates also differed. After six months, 54 percent of patients using the implantable device were alive, compared with 37 percent of those in the CMM-only group. The better survival among users of the implantable device may be partly explained by the fact that they experienced a larger reduction in toxic side effects, say the investigators, who were led by Thomas J. Smith, M.D., of the Medical College of Virginia in Richmond.

As many as 15 percent of cancer patients have pain that is not relieved by conventionally delivered narcotic pain medications, note the researchers. Previous studies have shown that fear of the side effects of these medications is an important reason why many doctors fail to prescribe them and many patients decline to take them.

"This is a well-designed study that shows a modest but real benefit from the use of an implantable pump for control of cancer pain," commented Mitchell Max, M.D., a pain control specialist at the National Institute of Dental and Craniofacial Research in Bethesda, Maryland. He added, however, that it is premature to conclude that implantable pumps are better for all patients with difficult-to-treat cancer pain. "We need more research to better define which subgroups of cancer patients will benefit the most from using these devices."

Glossary Terms

A small device installed under the skin to administer a steady dose of drugs.

A substance used to treat moderate to severe pain. Narcotics are like opiates such as morphine and codeine, but are not made from opium. They bind to opioid receptors in the central nervous system. Narcotics are now called opioids.

A study in which the participants are assigned by chance to separate groups that compare different treatments; neither the researchers nor the participants can choose which group. Using chance to assign people to groups means that the groups will be similar and that the treatments they receive can be compared objectively. At the time of the trial, it is not known which treatment is best. It is the patient's choice to be in a randomized trial.

The percentage of people in a study or treatment group who are alive for a certain period of time after they were diagnosed with or treated for a disease, such as cancer. The survival rate is often stated as a five-year survival rate, which is the percentage of people in a study or treatment group who are alive five years after diagnosis or treatment. Also called overall survival rate.