Although there is a huge body of scientific research on cancer biology, the quality and quantity of research on the management of cancer pain lags far behind, according to researchers at the New England Medical Center Evidence-based Practice Center (EPC) conducting a systematic literature review for the Agency for Healthcare Research and Quality (AHRQ). Overall, the EPC found that the solid evidence that exists on specific therapies such as anti-inflammatory drugs or opioids is overshadowed by inadequate guidance on more complex choices now expected of front-line clinicians.
In particular, the EPC found little research on quality of life in relation to pain control, drug interactions during long-term cancer pain treatment, the optimal sequence of adding drugs to improve pain control, how best to combine drug with non-drug therapies, and the impact that ethnicity has on cancer pain and patients' responses to treatment. Also, it found almost no analgesic drug trials in children with cancer pain.
"While there are many studies being conducted on cancer and the relief of pain resulting from cancer, this research clearly demonstrates that there are critical gaps in our knowledge," said John M. Eisenberg, M.D., director of AHRQ. "An important benefit of evidence-based research funded by AHRQ is to identify where we need to know more to improve what we can do for our patients."
Cancer pain affects the quality of life of large numbers of patients and their families, and adds substantially to the already considerable national disease burden of cancer. The EPC reported that vulnerable populationsminorities, women, children and the elderlycontinue to be at increased risk of being underassessed and undertreated for pain. Yet the EPC found that the number of patients enrolled in methodologically sound studies of cancer pain relief is a tiny fraction of those receiving care, about 1 in 10,000 patients, a much lower percentage than for nearly all other high-impact, costly conditions. In addition, the average number of patients enrolled per trial on cancer pain treatment often is too few to draw firm conclusions about the treatment under study. These new findings echo earlier calls by pioneers in the field to improve the quality and statistical power of clinical trials in cancer pain relief.
The EPC identified over 19,000 studies on the management of cancer pain. Following a rigorous screening process, only 24 epidemiologic surveys and 189 randomized controlled trials of treatments qualified for inclusion in their report. Despite the relative scarcity of high-quality studies, the EPC found specific evidence to indicate:
- Controlled release morphine and immediate release morphine solution are equally as effective at providing pain relief.
- Patients receiving rectal morphine have a slightly more favorable onset and duration of pain relief and experience less nausea than those treated orally.
- Celiac plexus nerve block for pain relief is effective in pancreatic and other visceral cancers.
- Hypnosis can help with procedure- and oral mucositis-related pain in adults and children.
The summary of Management of Cancer Pain is available in print from the AHRQ Publications Clearinghouse, P.O. Box 8547, Silver Spring, MD 20907, or by calling 1-800-358-9295. Copies of the full report are expected to be available from the Clearinghouse and on the NGC later in 2001.