Special, high-dose formulations of vitamin D and common, over-the-counter painkillers can greatly slow the growth of prostate cancer tumors, U.S. researchers reported Thursday.
Combining the two slowed their growth by up to 70 percent in a laboratory dish, the team at the Stanford University School of Medicine found.
Dr. David Feldman and colleagues are so impressed by the results that they have started a clinical trial to see if the approach also works in men.
“There is great enhancement when the drugs are given together, using what we think is a safe dose in humans,” Feldman said in a statement.
“It’s hard to make an exact comparison, as we are talking about cells in a dish and not a person.”
Feldman stressed that his team is testing calcitriol, a form of vitamin D that is efficiently used by the body and different from the sort found in vitamin pills and fortified milk.
“We don’t want the patient to think that if they take over-the-counter vitamin D, it will work in the same way,” Feldman said.
Writing in the journal Cancer Research, Feldman and colleagues said they have seen the effects of calcitriol before and, based on the cancer-slowing effects seen in some trials of painkillers, they wanted to see if the two approaches worked in synergy.
Using prostate tumor cells in lab dishes, they saw a 25-percent reduction in prostate-cell growth using only calcitriol, and about the same reduction using only ibuprofen and naproxen.
When they combined calcitriol and one of the two painkillers, they saw growth slow by as much as 70 percent.
Nearly 30,000 men die every year in the United States from prostate cancer and more than 200,000 are diagnosed.
The cancer is normally slow-growing but becomes aggressive in some men.
Feldman’s team plans to test the drugs in men whose prostate cancer has returned after surgery or radiation therapy.