Opiate-based painkillers like morphine can stimulate the growth and spread of cancer cells, revealed by researchers.
The new study is presented at “Molecular Targets and Cancer Therapeutics,” a joint meeting in Boston of the American Association for Cancer Research, the National Cancer Institute, and the European Organization for Research and Treatment of Cancer–highlight the mu opiate receptor, where morphine works, as a potential therapeutic target.
“If confirmed clinically, this could change how we do surgical anesthesia for our cancer patients,” said Patrick A. Singleton, PhD, assistant professor of medicine at the University of Chicago Medical Center and principal author of both studies. “It also suggests potential new applications for this novel class of drugs which should be explored.”
The proposition that opiates influence cancer recurrence, prompted by several unrelated clinical and laboratory studies, has gradually gained support. It started with a 2002 palliative-care trial in which patients who received spinal rather than systemic pain relief survived longer. Soon after that, Singleton’s colleague, anesthesiologist Jonathan Moss, noticed that several cancer patients receiving a selective opiate blocker in a compassionate-use protocol lived longer than expected. Two recent retrospective studies found that breast and prostate cancer patients who received regional rather than general anesthesia had fewer recurrences. In February, 2009, the Anesthesia Patient Safety Foundation highlighted the issue.
“These were patients with advanced cancer and a life expectancy of one to two months,” Moss recalled, “yet several lived for another five or six. It made us wonder whether this was just a consequence of better GI function or could there possibly be an effect on the tumors.”
So Singleton, Moss and colleagues, including Joe G.N. Garcia, MD, professor of medicine at the University of Chicago, began a series of studies looking at the many peripheral effects of opiates and the potential benefits of blocking those effects.
In laboratory studies, morphine can directly boost tumor-cell proliferation and inhibit the immune response. The researchers found that opiates also promote angiogenesis, the growth of new blood vessels, and decrease barrier function–effects that may exacerbate diseases involving vascular leakiness including acute lung injury in experimental models. In a surgical setting, decreased barrier function may make it easier for tumors to invade tissue and spread to distant sites. Increased angiogenesis helps cancers thrive in a new site.
“In conjunction with previous studies on opiate-induced angiogenesis by our laboratory and others, these experimental data suggest a plausible explanation for the epidemiologic observations,” notes Moss, professor of anesthesiology and critical care at the University of Chicago. “If these laboratory studies are confirmed clinically, the selection of anesthetic technique used during the operative procedure and the possible use of opiate antagonists in the perioperative period may be important.”
Source: University of Chicago Medical Center, USA