Does Morphine Encourage Cancer Growth?

Thomas Quinn, APRN, MSN

• The news reports were based on a press release by the University of Chicago press office.  It should be noted that methylnaltrexone, which is currently indicated only for opioid-induced constipation in advanced cancer patients, was developed at the University of Chicago and licensed to a pharmaceutical company.
  
  
• The press release is based on a presentation at a scientific meeting.  Even early research findings by well-regarded scientists must be subjected to peer review through publication in reputable scientific journals; this report is yet to be published.
  
  
• The research was initiated after a small number of patients in a methylnaltrexone study lived longer than expected.  Similarly, a very small number of patients with advanced cancer in an intrathecal analgesic study lived a little longer than expected (but did not reach statistical significance, and it was not a study end-point).
  
  
• Three small, single-institution clinical studies are mentioned (two of them at the same institution in Ireland).  Longevity related to opioid use was not a study question in any of these studies.  There are multiple other factors that could have contributed to any perceived survival advantage.
  
  
• There are several small studies which show that well-managed pain (using aggressive opioid treatment) in end-stage disease does not shorten life and may have a slight survival advantage in some cases (these studies did not address the direct affect of opioids on tumor growth, which is the presumed reason for the observed survival effect). 
  
  
• Opioid analgesics have a long and well-documented track record of relieving pain and dyspnea associated with advanced cancer, reducing suffering, and improving quality of life.