Clues to aggressive prostate cancer

Hopkins study finds less disease in men with low cholesterol

November 23, 2006|By Jonathan Bor | Jonathan Bor,Sun reporter

In a season of ritual overeating, Johns Hopkins researchers have come up with another reason for men to watch their diets: Low cholesterol might protect them from the most aggressive form of prostate cancer.

This isn't the first time medical researchers have linked fats to cancer and its consequences. Recent studies have linked obesity to higher death rates from several types of cancer, and a previous Hopkins study found that men on cholesterol-lowering drugs were less likely to develop fast-growing prostate tumors.

Now, researchers led by epidemiologist Elizabeth Platz report that men in a study with low cholesterol were one-third less likely to get high-grade prostate cancer - the type that tends to grow quickly and spread.

"We already know that maintaining a good range of cholesterol concentrations is important for cardiovascular health," said Platz of the Johns Hopkins Bloomberg School of Public Health and the Hopkins Kimmel Cancer Center.

"Now, we know there may be a benefit for other diseases, possibly prostate cancer."

The research was part of a continuing Harvard University study of 18,000 health professionals. That study investigates possible links between nutrition and chronic disease.

In 1993, researchers asked the men to submit blood specimens through the mail. More than 18,000 did so, and their specimens were put in cold storage. Later, the researchers identified 700 men who developed prostate cancer and compared their blood with that of 700 men without evidence of the disease.

The scientists found no difference in the cholesterol levels of men with and without prostate cancer. But they did discover that men with low cholesterol were less likely to get aggressive cancers.

"What we're thinking is that cholesterol doesn't seem to influence the initial development of the disease," Platz said. "Maybe it affects the progression of the disease and the differentiation status" - alterations in the prostate cells when they become aggressively cancerous.

Viewed under a microscope, the cells of high-grade prostate tumors tend to clump together and lose their distinct, orderly appearance. For patients, these cells are more likely to break out of the prostate gland and spread to other tissues, where they can prove fatal.

Men with high-grade prostate cancer are also more likely to have a recurrence after having their prostates surgically removed.

According to Platz, men do not have to be concerned about lowering their cholesterol to abnormal levels. Those less likely to develop aggressive tumors had cholesterol levels in the range that's considered healthy for the cardiovascular system.

Overall, men whose cholesterol levels were no greater than 165 milligrams per deciliter of blood had the lower rates of high-grade prostate cancer. Platz, however, warned against interpreting this as a benchmark, saying the threshold differed among subgroups.

What the low-risk men had in common is that their cholesterol levels fell in the lowest fourth - or quartile - of the total group's. In a curious twist, researchers found that the risk of developing aggressive tumors was about the same at all higher levels; it didn't grow worse as cholesterol levels rose through the spectrum.

The scientists decided to study cholesterol levels after finding that men who took statins - a class of cholesterol-lowering medications - ran about half the risk of advanced prostate cancer as men not on the drugs. The researchers, however, don't suggest taking statins solely for cancer prevention.

"It did say to us that there was something about cholesterol that may be of interest for prostate cancer," Platz said.

Eric Jacobs, senior epidemiologist with the American Cancer Society, said the results of the latest study were exciting. But he agreed with Platz that more research was needed to establish a clear connection between cholesterol and prostate cancer.

"We're not there yet," Jacobs said. "Stay tuned."

Even so, he said evidence is growing that diet could play an important role in prostate cancer. Numerous studies in recent years have shown that obese men are more likely to develop the advanced disease.

In 2003, a large study published in the New England Journal of Medicine found that obese men and women had higher death rates from all cancers combined, as well as individual cancers of the esophagus, colon, liver, pancreas, kidney - and prostate.

Also, studies have shown that obese men who develop less advanced prostate cancer are more likely to suffer a recurrence after cancer treatment.

But, as is often the case in medicine, the picture is clouded. In an earlier piece of the Harvard health professionals study, scientists found that the risk of prostate cancer was actually lower in two categories of obese men - those under 60 and others with a a family history of prostate cancer.

Some scientists speculated that tumors in these men are strongly influenced by male hormone and that the heavier men benefited from having reduced male hormone.

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