FRIDAY, June 6, 2003 (HealthDayNews) -- Vitamin D could hold a clue to more effective breast cancer treatment.
That's the suggestion put forward by a group of Dartmouth researchers in a report in the June issue of the Journal of Clinical Cancer Research.
The study, which involved the treatment of breast cancer tumors in mice, adds to a growing body of evidence that a derivative of vitamin D known as EB1089 may yield some powerful anti-cancer properties, particularly when combined with radiation therapy.
"When compared to other cancer treatments, the vitamin D analog is much less toxic and, at least preliminarily, it appears to aid radiation therapy in impacting the growth of tumor cells," says study author Sujatha Sundaram, a research assistant professor at Dartmouth Medical School.
An analog is a synthetic, laboratory-made version of a parent compound -- in this case vitamin D -- that is genetically engineered by adding or removing certain chemical elements. In the instance of EB1089, it was necessary to modify vitamin D because "at the dose you need to give to have an effect on cancer, it could cause some side effects," Sundaram says. Those side effects would include an overload of calcium, a condition known as hypercalcaemia.
The analog used in the study, Sundaram says, has little or no toxic reaction, even in high doses.
Adding the vitamin D to the treatment regimen is thought to enhance the ability of the radiation to bring about apoptosis -- or cell death. It also reduces the proliferation, or growth of cancer cells, in the tumor itself, Sundaram explains.
"These are all things that radiation therapy can accomplish on its own. But the EB1089 appears to make the treatment more effective, possibly reaching pockets of cells that might otherwise be missed, or in encouraging apoptosis in cells that for one reason or another might be stubborn or resistant to the effects of the radiation," Sundaram says.
While the finding in this particular study is unique, previous research on vitamin D found it was effective against both prostate and breast tumors. Currently, a large European trial is testing EB1089 on human cancer patients.
For radiation oncologist Dr. Victor Ayzenberg, the study results and the compound offer hope.
"It's a very good study, with important information. It would be great if we can use it with patients," says Ayzenberg, a clinical professor of medicine at the Mount Sinai School of Medicine in New York City.
It's a simple idea, he adds, but it clearly has merit.
The new study was small, involving just eight mice, each implanted with human breast cancer cells. When tumors reached approximately 200 millimeters in size, half the mice received an infusion pump with a continuous flow of EB1089 for eight days. The other mice received a pump containing a harmless solution.
After a few days rest, both groups of mice received three "fractions" -- or doses -- of radiation therapy over the course of three days. The tumors were then monitored for 25 to 30 days, checking for both size and spread.
The result: The mice treated with EB1089 had a far faster rate of tumor regression, with tumors shrinking to a much smaller size. In the final analysis, the tumors in the mice receiving EB1089 plus radiation were approximately 50 percent smaller than those receiving radiation alone.
In addition, Sundaram says, there was less cancer cell proliferation -- or cell growth -- in the mice treated with the vitamin D analog. This, she says, indicates that EB1089 not only helped encourage apoptosis of the tumor cells, it also blocked new tumor cell growth.
As encouraging as the findings are, Sundaram stresses cancer patients should not assume that vitamin D supplements will have the same effect. And she warns that overloading on supplements could be dangerous.
More information
To learn more about radiation therapy, visit The American College of Radiology. For more on breast cancer, check with the National Institutes of Health.
