(Chicago, IL)  --  U.S. researchers are seeing growing evidence that morphine and similar pain management drugs may encourage tumors to grow and spread.

   The negative effects of opiate-based painkillers on cancer patients took center stage Wednesday at the Molecular Targets and Cancer Therapeutics meeting in Boston.

   At the meeting, Patrick Singleton of the University of Chicago Medical Center pointed to a 2002 study that found cancer patients who received morphine injections only in the spine tended to live longer than those who had the drug coursing through their entire bodies.

   He also cited two recent unrelated studies that found patients with breast and prostate cancer who received regional anesthesia were less likely to have the cancer come back than those who underwent general anesthesia.

   Singleton also presented two studies that indicate a drug from Progenics Pharmaceuticals may reverse the tumor-causing effects of opiates without changing their anesthetic qualities.

   The drug Relistor is used to treat constipation and other side effects of drugs like morphine.

   However, Singleton and colleague Jonathan Moss also found that the drug's ability to block opiate receptors on lung tumor cells kept the cancer from spreading in lab dishes.

   A second study conducted by the team found that Relistor reduced the spread of lung cancer cells in normal lab mice by 90-percent.



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