Good Evidence Supporting the Use of Opioids for Treating Cancer Pain

Systematic literature review confirms that a range of opioid formulations and delivery methods provide safe and effective treatment options for cancer pain.

Systematic literature review confirms that a range of opioid formulations and delivery methods are safe and effective treatment option for cancer pain.

Studies show that at least one-third of patients diagnosed with cancer report pain associated with their disease. This figure increases to as high as 90% in patients with advanced illness. In addition to pain caused by the malignancy itself, many patients also report pain stemming from a range of cancer treatments.

Although there are currently many effective treatments available for cancer pain (with opioids being the “gold standard” for treating moderate to severe cancer pain), the authors of “A Systematic Review of Observational Studies on the Effectiveness of Opioid Therapy for Cancer Pain,” published in the March 2011 issue of Pain Physician, note that “inadequate treatment of chronic cancer pain persists despite decades of efforts to provide clinicians with information about analgesics and pain-relieving techniques.”

They attribute this situation to a variety of patient-related (eg, “underreporting, fear of disease progression, poor compliance with prescribed medications) and physician-related factors (eg, “legal issues with misuse, abuse, overuse of prescription medications, difficulty assessing pain complaints, lack of information, or lack of expertise).

Whereas the approach to treatment of chronic non-cancer pain suffers from a relative lack of relevant effectiveness data, especially where the use of opioids is concerned (leading to the present state of affairs of opioid overuse accompanied by widespread abuse, misuse, and diversion), the picture is different for treating cancer pain. The effectiveness of opioid medications in the treatment of cancer pain “has been evaluated in multiple randomized trials and systematic reviews” (although the authors of this article do cite a lack of larger trials with longer follow-up periods). If anything, cancer pain is undertreated, and is not characterized by the same problems with opioid abuse.

However, the authors caution that “the future of evidence-based medicine for cancer pain management continues to be poorly addressed, despite the effectiveness of opioids in managing chronic cancer pain rather effectively.” To address these shortcomings, it is “essential to conduct randomized and non-randomized trials to establish the efficacy of opioids in managing chronic cancer pain, which will also provide data on the dose responses and treatment of breakthrough pain.”

Accordingly, to “provide an updated assessment of the current literature for evidence-based criteria for the overall effectiveness of opioid therapy in managing cancer pain,” and identify several potential shortcomings to be addressed in future trials, the authors conducted a comprehensive systemic search of the literature published between 1996 and 2010 for observational clinical trials involving adults patients “being treated for cancer-related pain of any duration with any opioid, administered by any route with or without concomitant ancillary medications.” Eligible trials included at least a three-month follow-up period, with primary outcome measures of efficacy of pain relief and overall safety.

The authors assessed each study using the Agency for Healthcare Review and Quality (AHRQ) criteria for observational studies and the weighted scoring criteria developed by the American Society of Interventional Pain Physicians (ASIPP) guidelines committee. They analyzed the studies using the five levels of evidence developed by the United States Preventive Services Task Force (USPSTF). A total of seven studies with at least 50 participants and three months or more of follow-up met the inclusion criteria for methodologic quality assessment. Based on their AHRQ scores, three of the studies were rated as being of “moderate quality,” with the other four rated as being of “high quality.”

Analysis of the data from studies included in this report indicates that the use of transdermal opioid delivery systems primarily (especially fentanyl, and buprenorphine) “shows promise” for treating cancer pain. The authors note that several studies that did not meet their inclusion criteria nonetheless have shown that transdermal fentanyl is an effective and safe treatment option for cancer pain. Likewise, this review confirmed that sustained-release opioid formulations (the “mainstay for analgesic maintenance in cancer pain management”) are also safe and effective for treating cancer pain. The data also show that treatment for breakthrough cancer pain using “oral preparation of fentanyl formulated to maximize rapid onset with short duration of effect” is effective and well-tolerated.