Dr. John Ruckdeschel, director of the University of Mississippi Medical Center’s Cancer Institute, discusses pain management. Wochit
Opioids used to relieve cancer pain may be causing some tumors to grow and spread, some studies suggest.
It’s potentially disturbing because more than 1.6 million Americans are diagnosed with cancer each year, and those who suffer debilitating pain are often prescribed opioids for relief.
Last month, international experts huddled at M.D. Anderson Medical Center in Houston to discuss improving care for cancer patients, including the best ways to utilize opioids.
One of those experts was Dr. Jonathan Moss. He worked on a University of Chicago study that showed that human lung cancer cells with additional opioid receptors grow more than twice as fast as tumor cells without extra receptors when transplanted into mice. These lung cancer cells were also 20 times more likely to spread to distant sites.
A companion University of North Carolina study, which looked at more than 2,000 breast cancer patients, found that women with a mutation of the opioid receptor that made them less sensitive to opiates were much more likely to be alive a decade after cancer treatment.
“There is no evidence that opioids cause cancer," Moss told the USA TODAY NETWORK, "but there is animal and human evidence that commonly used opiates are associated with tumor progression in certain tumors, including advanced prostate cancer."
Blocking these opioid receptors with drugs “is associated with improved survival in patients with several different types of cancer," he said.
He has helped develop an antagonist aimed at blocking side effects of opioids.
A 2017 review of studies over the past two decades for the Pain Medicine journal concluded that morphine has “a potential causal relationship” with the spread of cancer and the growth of new blood vessels to feed these tumors.
Co-author of the review, Dr. Alaa Abd-Elsayed, medical director of the University of Wisconsin Health Pain Services, suggested oncologists and pain management doctors examine alternatives to opioids.
Because there have been so few human studies on this issue, the majority of experts are urging medical providers to take a “wait-and-see” attitude before making any changes.
Dr. John Ruckdeschel, director of the University of Mississippi Medical Center’s Cancer Institute, warned that what sometimes looks like causation often turns out to be correlation.
He recalled designing and co-chairing a national study that began because researchers had given selenium (found in baker’s yeast) to patients for the prevention of melanoma. Although selenium had no effect on melanoma, researchers noticed less lung cancer.
“We put together a huge national trial,” he said. “We gave several thousand patients selenium and the same number of patients a placebo.”
In the end, “there wasn’t a spit’s bit worth of difference,” he said. “We just published that recently (in the Journal of Clinical Oncology)."
He said something similar happened in the 1980s when researchers examined whether consuming vitamin A would prevent cancer development.
In the end, not only did the vitamin A derivatives not help, “they hurt,” he said. “Those people got more cancers.”
He sees three categories for pain: acute, chronic and chronic acute as seen in cancer patients.
He said acute pain occurs when someone accidentally hits his thumb with a hammer, causing tissue damage, but chronic pain, such as lower back pain, may not be detectable through tests.
For those suffering from cancer, the pain may feel like whacking the thumb each day with the same hammer, he said.
He said he remains concerned that the crackdowns on opioid abuse could keep painkillers out of the hands of cancer patients who desperately need them. “Undertreatment of pain is the big problem in oncology.”
While a possible link between opioids and tumor growth isn't clear, physicians are less concerned about fostering an opioid addiction with cancer patients.
Ruckdeschel said addiction is rarely seen among cancer patients. A 2007 review of studies put the risk of addiction among cancer patients at less than 8 percent.
In comparison, a Centers for Disease Control and Prevention study of non-cancer patients found the odds for becoming a long-term opioid user increase to 1 in 5 after just 10 days of taking the painkillers. After 30 days, the odds rise to nearly 1 in 2.
Although the numbers are lower for cancer patients, addiction does occur, Abd-Elsayed said. “I have seen cancer patients addicted to opioids. We should still be monitoring and protecting our patients.”
Dr. Reid Blackwelder, past president of the American Academy of Family Physicians, said doctors desiring to treat their patients with something other than painkillers can find it difficult because many insurers won’t cover alternatives, such as physical therapy and acupuncture.
On top of that, high deductibles in many insurance plans discourage patients from seeing their doctor to start with, he said. “We still do not see people in our office early enough to be proactive in managing almost any problem.”