Background: In all recommended guidelines put forth for the treatment of cancer
pain, opioids continue to be an important part of a physician’s armamentarium.
Though opioids are used regularly for cancer pain, there is a paucity of literature
proving efficacy for long-term use. Cancer is no longer considered a “terminal
disease”; 50% to 65% of patients survive for at least 2 years, and there are about
12 million cancer survivors in the United States. There is a concern about side effects,
tolerance, abuse and addiction with long-term opioid use and a need to evaluate the
effectiveness of opioids for cancer pain.
Objective: The objective of this systematic review was to look at the effectiveness of
opioids for cancer pain.
Study Design: A systematic review of randomized trials of opioids for cancer pain.
Methods: A comprehensive review of the current literature for randomized controlled
trials (RCTs) of opioids for cancer pain was done. The literature search was done using
PubMed, EMBASE, Cochrane library, clinical trials, national clearing house, Web of
Science, previous narrative systematic reviews, and cross references. The studies were
assessed using the modified Cochrane and Jadad criteria. Analysis of evidence was
done utilizing the modified quality of evidence developed by United States Preventive
Services Task Force (USPSTF).
Outcome Measures: Pain relief was the primary outcome measure. Secondary
outcome measures are quality of life (QoL) and side effects including tolerance and
addiction.
Results: The level of evidence for pain relief based on the USPSTF criteria was fair
for transdermal fentanyl and poor for morphine, tramadol, oxycodone, methadone,
and codeine.
Limitations: Randomized trials in a cancer setting are difficult to perform and justify.
There is a paucity of long-term trials and this review included a follow-up period of
only 4 weeks.
Conclusion: This systematic review of RCTs of opioids for cancer pain showed fair
evidence for the efficacy of transdermal fentanyl and poor evidence for morphine,
tramadol, oxycodone, methadone, and codeine.
Key words: Opioids, pain relief, cancer pain, morphine, hydromorphone, methadone,
fentanyl, oxymorphone, hydrocodone, oxycodone, buprenorphine.
Electrical stimulation for pain relief in knee osteoarthritis: systematic review and network meta-analysis
