The finding that mice with advanced human prostate cancer that were deprived of testosterone and fed a diet low in polyunsaturated fats had slower tumor growth and an improvement in survival of almost 2-fold may translate to better care for men with the disease, according to an article in the February 15th issue of Cancer Research.

Dr. William Aronson, the lead author of the study, also noted that the mice on the low-fat diet had persistently lower levels of prostate-specific antigen than matched mice fed a more traditional, higher-fat diet.

“These results provide a sound basis for clinical trials evaluating the impact of dietary fat reduction in prostate cancer patients on hormone therapy,” said Aronson. “This new finding tells us that a low-fat diet can impact cancer growth and survival times in laboratory mice. We need to understand why, and duplicate the results in humans.”

In the current study, the American investigators chose to a baseline diet similar to that commonly eaten in the U.S., specifically, a diet high in polyunsaturated fats derived from corn oil such as those found in bakery products and fried foods. They then applied the baseline and trial diet to mice with advanced human prostate cancer that were being treated with hormone-deprivation therapy.

The mice were divided into 3 groups: The first was fed a high-fat diet containing about 42 percent of calories from polyunsaturated fats. A second group was castrated ? to mimic men on androgen deprivation therapy ? and fed a diet with 42 percent of calories from fat. The third group of mice (also castrated) was fed a low-fat diet, with about 12 percent of calories coming from fat. All three groups ate the same total number of calories.

The uncastrated mice in the high-fat diet group died quickly from the disease. Tumor growth in the castrated mice fed a high-fat diet stabilized for a time ? mirroring what happens to men with advanced prostate on hormone therapy. As expected, and as often happens in humans, the cancers in these mice then began to grow again. Meanwhile, the castrated mice on a low-fat diet went twice as long before their cancers became androgen independent and began to grow again.

Additionally, survival times were significantly longer in the low-fat diet group, and tumor size was much smaller than those found in mice on a high-fat diet, Aronson said.

“This study may help us solve a clinical problem, how to prevent or delay androgen independence,” Aronson said. “Now we need to do more detailed laboratory studies to find out how the fat intake is affecting the growth of the androgen independent cancers.”

Doctors have been recommending a diet low in fat for some time, based on epidemiological studies offering evidence that such eating habits may help prevent certain cancers. This study is the first to show that a low-fat diet may help hormone therapy work better and longer, Aronson said. Although human trials are several years away, he recommended that men with prostate cancer switch to a low-fat diet (15-20 percent of calories from fat) and combine diet with daily exercise.

“I think dietary fat reduction, coupled with high fiber intake from fruits and vegetables in a variety of colors, can truly have an impact on prostate cancer prevention, and in combination with existing treatments, perhaps increase survival times for patients,” Aronson concluded.