Researchers examining the data on opioid medicines have found surprisingly large gaps in evidence regarding the true benefits of these medicines for cancer pain.
The review challenges the commonly held view that opioid medicines are the most powerful cancer pain relievers.
The University of Sydney-led review highlights there is no ‘one size fits all’ treatment approach for treating pain from cancer, urging health professionals and patients to carefully weigh up the evidence when deciding on a suitable pain management plan.
The research, ‘Opioid analgesics for nociceptive cancer pain: A comprehensive review,’ is published in CA: A Cancer Journal for Clinicians.
Could pain relief from opioids be a placebo effect?
Opioid pain relievers are the most common treatment for cancer pain management. Many international guidelines, including the World Health Organization, recommend opioid medicines to manage background cancer pain (constant pain) and breakthrough cancer pain (temporary flare-ups of pain in addition to background pain).
However, the study found very few trials have compared commonly used opioid medicines such as morphine, oxycodone and methadone with placebo.
The study did not find convincing evidence that morphine was better or safer than other opioids for background pain from cancer outside of end-of-life care.
This is despite morphine being widely viewed as the ‘gold standard treatment’ for cancer care by physicians and recommended in many international clinical guidelines for moderate to severe cancer pain because of its low cost and accessibility.
“The lack of evidence comparing opioid medicines to placebo for cancer pain probably reflects the ethical and logistical challenges associated with carrying out such trials. Yet these trials are necessary to guide clinical decision making,” said lead researcher Dr Christina Abdel Shaheed from the University of Sydney School of Public Health, Faculty of Medicine and Health and Sydney Musculoskeletal Health.
Other pain relievers could be just as effective as opioid medicines
The review also found that non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin and diclofenac, may be at least as effective as some opioids for background cancer pain.
Co-author Professor Jane Ballantyne from the University of Washington School of Medicine explained: “In practice, opioid medicines are indispensable for intractable pain and distress at the end of life.
“What is worth highlighting is that non-opioids, particularly NSAIDs, are surprisingly effective for some pain from cancer and may avoid the problems of dependence and waning opioid analgesia over time.”
Co-author Professor Martin Underwood from the University of Warwick concluded: “People with background cancer pain may have an overall better life experience if there is less focus on using opioids to reduce their pain level.”
