Effect of Opioids on Survival in Patients with Cancer

SIMPLE SUMMARY: Opioids, such as morphine, are strong pain killing medicines. Patients with cancer often need opioids to manage their pain. Although they might be helpful for pain control, opioids have side effects. Some of these side effects are obvious such as constipation and confusion. Other side effects are less overt, such as effects on the immune system and other effects on cancer growth. There have been studies in patients with advanced cancer which show that patients taking opioids have a shorter survival than patients not taking opioids. There are other differences in these groups of patients which might also account for the differences in survival. These include the possibility that patients needing opioids might have more aggressive cancers which cause more pain, which is why this group of patients take more opioids. It is also possible that the more aggressive cancer is what shortens survival. Future studies are needed to understand the cause of the effects of the underlying cancer type, pain, specific opioids, and survival. Until this is better understood, opioids should continue to be used to control pain in patients with cancer. ABSTRACT: Opioids are commonly used for pain management in patients with cancer. They have a range of unwanted effects, including some that potentially influence cancer growth. This article reviews the data assessing the effects of opioids on survival in patients with cancer. Many studies assessing this show an association between opioids and decreased survival. This effect is present even at very low doses of opioids. These studies do not assess causality, so it is not known if it is a direct effect of opioids on survival. As the control groups are not matched to the opioid group it might be that opioids are being used to control pain and patients receiving opioids have more aggressive cancers and it is the underlying cancer which is causing the decreased survival. Furthermore, although some studies allude to different opioids having different effects on survival, often all opioids are pooled in analysis. Future work needs to try to ascertain causality and differentiate between different opioids, pain, and cancer-mediated effects on survival in specific cancer types. Until then, opioids should continue to be used in patients with cancer as part of measures to optimise comfort and quality of life.