Morphine could 'spread cancer'

Morphine given to cancer patients may cause their disease to worsen, or to spread to other parts of their body, according to new US research.

The researchers said that morphine appeared to promote the growth of new blood vessels around tumours.

They said they had found a drug which counteracted the cancer-promoting side effects of morphine.

Patrick Singleton, assistant professor of medicine at the University of Chicago in the US, said that morphine appeared to make it easier for cancers to invade other tissues, though a drug named methylnaltrexone (MNTX) appeared to work against morphine's side effects on blood vessel formation without interfering with pain relief.

MNTX was developed in the 1980s for opiate-induced constipation by a pharmacologist at the University of Chicago named Leon Goldberg. Goldberg modified an established drug that blocks morphine.

The resultant drug, MNTX, is able to block the action of morphine in the body, but not in the brain. Using MNTX, the researchers were able to inhibit the morphine-related spread of cancer in their patients by up to 90%.

Singleton said the finding could change the way in which surgeons anaesthetise patients. He said that the finding also suggested new applications for a new class of drugs.

The researchers began their study when one of Singleton's colleagues named Jonathan Moss noticed that some cancer patients receiving MNTX in his palliative-care unit survived longer than expected.

Moss said that the patients who survived longer on MNTX were patients with advanced cancer and a life expectancy of one to two months.

He said that, because several of them lived for another five or six years, he and his colleagues wondered whether the drug's action was just a consequence of better GI function.

Laura Bell of Cancer Research UK said it was too early to tell whether opiate-based painkillers had an effect on cancer growth.

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