A comprehensive review of opioid use for cancer-related pain has revealed significant gaps in evidence regarding the actual benefits of these medications.
Contrary to the prevailing belief that opioids are the most potent pain relievers, the University of Sydney-led review suggests a nuanced approach to cancer pain management, emphasizing the absence of a one-size-fits-all solution.
Opioid pain relievers are widely prescribed for cancer pain management, with international guidelines, including those from the World Health Organization, endorsing their use for background cancer pain (constant pain) and breakthrough cancer pain (temporary flare-ups in addition to background pain).
However, the study found a notable scarcity of trials comparing commonly used opioid medications, such as morphine, oxycodone, and methadone, with a placebo. Surprisingly, there was insufficient evidence to establish that morphine was superior or safer than other opioids for background cancer pain, contradicting its widespread perception as the "gold standard treatment" for cancer care.
The review also suggested that non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin and diclofenac, may be equally effective as certain opioids for background cancer pain.
The lead researcher from the University of Sydney School of Public Health emphasized the ethical and logistical challenges associated with conducting trials comparing opioid medicines to placebos for cancer pain. Despite these challenges, such trials are deemed crucial for informing clinical decision-making.
Co-author Professor from the University of Warwick highlighted the potential for a better overall life experience for individuals with background cancer pain if there is less emphasis on using opioids to reduce pain levels.
The study's findings may guide doctors and patients in choosing between different opioid treatments for cancer pain and encourage consideration of alternatives, especially for those unable to tolerate or choosing not to take opioid medicines.
The analysis incorporated data from over 150 published clinical trials. Few trials compared opioid medicines to placebos, but evidence suggested that tapentadol might be more effective than a placebo for background pain caused by cancer. Opioids considered weaker (e.g., codeine), NSAIDs like aspirin, piroxicam, ketorolac, diclofenac, and the antidepressant imipramine were found to be comparable to potent opioids for background cancer pain with fewer side effects.
For breakthrough cancer pain, fentanyl, administered through various methods, was identified as potentially more effective than a placebo, albeit with more side effects. The study also called for research to investigate potential negative interactions between opioid medicines and anti-cancer treatments or the immune system to ensure that pain management does not compromise cancer treatment effectiveness. Additional research on non-drug interventions for cancer pain management was deemed necessary.
