A drug that is given to late-stage cancer patients to help ease the constipation brought on by morphine has been shown to extend their lives, researchers report.
Methylnaltrexone, approved by the US Food and Drug Administration in 2008 to treat opioid-induced constipation, could play a role in cancer therapy, said researchers who presented their findings at the meeting of the American Society of Anesthesiologists in San Diego.
"Early on, we began to suspect that methylnaltrexone might inhibit cancer growth," said Jonathan Moss, lead author of the study and professor of anesthesia and critical care at the University of Chicago.
"After more than a decade in the lab trying to assess how methylnaltrexone affects cancer, we have the first evidence that it can decrease tumour growth and extend survival in patients who respond to the drug."
The study was a retrospective survival analysis involving 229 patients across two randomised, controlled clinical trials on the relief of constipation for patients in the late stages of cancer and other terminal diseases.
Opioids like morphine are known to cause severe constipation that often cannot be relieved by traditional laxatives.
"In these two trials, 117 cancer patients received methylnaltrexone (marketed as Relistor) for opioid-induced constipation, while 112 were given a placebo," said the study.
Just 57 percent of those who received methylnaltrexone experienced relief from constipation. The other 43 percent did not.
"Those who received and responded to methylnaltrexone lived, on average, twice as long (118 days versus 58 days) as those who did not respond or were given the placebo," said the findings.
The drug did not have any life-extending effects on patients with other illnesses like congestive heart failure, advanced chronic obstructive pulmonary disease or neurologic diseases.
Researchers are not sure exactly how the drug works to extend life, and are continuing to study the matter.
Methylnaltrexone was invented in 1979 by Leon Goldberg, a pharmacologist at the University of Chicago who wanted to help a friend suffering from cancer and morphine-related constipation.
Moss and his colleagues began to notice in 2002, during early studies using the drug, that some cancer patients lived longer than expected.
"These were patients with advanced cancer and a life expectancy of one to two months yet several lived for another five or six months," Moss said.
"It made us wonder: could there possibly be a direct effect on the tumours?"
Next, researchers hope to find out if their discovery could lead to new methods of cancer treatment.