Does Morphine Encourage Cancer Growth?
Thomas Quinn, APRN, MSN
Some recent scary headlines in the lay press hyped a very preliminary study in lung cancer cell lines, suggesting that use of morphine (or other opioids) in advanced cancer patients may hasten death, and that methylnaltrexone, a peripherally acting opioid antagonist, may retard cancer growth. The news reports cite "growing clinical evidence" of this phenomenon. Unfortunately, the "clinical evidence" cited is barely tenuous and the laboratory studies are very preliminary.
- 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.
Clinical practice in any arena should not be changed based on the findings of a single study, even one that is well-designed and conducted. The findings from these studies are speculative. From a research perspective they raise interesting questions that suggest hypotheses and form the basis for future laboratory research. Based on results of those future studies, clinical trials can then be designed.
There is some fascinating science at work in this, and it will be prudent to follow its progress in the coming years. However, it would be imprudent, at best, to change current pain management practices with opioid analgesics based on this report. Patients and clinicians need to have the news reports put in perspective.
In the News
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