Lifelong Weight Control a Key to Breast Ca Prevention

Washington—Available methods to prevent breast cancer might be bettered compared to a flu shot “which hurts and only lasts a year,” than to a polio vaccine, “which comes on a sugar cube and lasts a lifetime,” Malcolm C. Pike, PhD, said at the Department of Defense’s “Era of Hope” meeting.

The sugar cube scenario “is not going to happen,” he said, but lifelong attention to diet and weight control, and development of better chemopreven-tives offer hope that breast cancer risk can be reduced.

“We need to think our way into this,” said Dr. Pike, of the Department of Preventive Medicine, University of Southern California. “We can explain a lot about why breast cancer develops, but maybe we just don’t like the answer.”

A realistic model of breast cancer risk reduction is not polio and an easy-to-take vaccine, but lung cancer and smoking cessation, Dr. Pike said. “Anyone who has smoked knows that just saying ‘Give up smoking’ is not a simple request.”

He cautioned against using the guilt-inducing tactics that has turned smokers into “the bad guys,” while approving the evolution of attitudes that has made smoking in public less and less acceptable. “If you want to do something about preventing breast cancer today, you’d make it more difficult to overeat in public,” he joked.

While telling people to eat five servings of fruits and vegetables a day is easy, it’s a lot harder—for cultural or financial reasons—to make a healthy diet accessible. “People want that polio model,” Dr. Pike said. “They’d rather take a beta-carotene pill than eat a healthy diet.”

Is It Weight or Soy?

He coupled questions of weight and hormones by pointing to the historic differences between breast cancer rates in the United States and Japan. “Breast cancer is a disease of functioning ovaries,” he said. “Traditional Japanese women entered menarche at 16 and weighed 95 pounds as adults.”

Dr. Pike said that these Japanese women start ovulating 2 or 3 years later than American women and also produce lower levels of estrogen throughout life.

He discounts a diet rich in soy as an explanation for the differences in breast cancer rates. Even the quantity of soy products eaten in East Asian diets is insufficient to explain the differences. Rather, he believes that weight is the issue.

“In the United States,” he said, “the Nurses Health Study showed that women who are at least 38 pounds overweight have a 50% increased risk of breast cancer. Losing weight has a rapid effect on breast cancer rates. This is something that can be done now.”

He noted, too, that exercise can lower risk by metabolizing estrogen, but said that questions remain about how much exercise is needed, how intensive it must be, and at what age it is important.

Hormone replacement therapy after menopause helps prevent heart disease and osteoporosis but increases breast cancer risk. “We need an improved tam-oxifen [Nolvadex]—a drug with the same properties but that will not stimulate the endometrium,” Dr. Pike said.

Since having an early full-term pregnancy is also protective, the best idea is to have a baby at 18. This is unlikely to happen since young women are, quite rightly, more interested in education and careers during their 20s, he said.

“We need to find the biochemical markers that let us know that the breast has had a full term pregnancy,” he said, “and then develop an agent that tells the breast the same thing. This is worth a lot of effort.”

Redesign the Pill?

The effects of oral contraceptives in reducing the incidence of ovarian cancer also bear examination, he said. “The biggest chemopreventive in this country is oral contraceptives, and you never hear about it,” he said.

Cancer of the ovaries has dropped by one-quarter in the last 20 years—due entirely to the pill, he believes. The average American woman on the pill uses it for 6 years. “The reason for this drop in ovarian cancer is that the pill puts the ovaries to rest,” he said.

He suggested the development of a pill that could be taken long term for contraception and/or breast cancer prevention. This would involve cutting the amount of estrogen in the pill by 50% and progestin by 80%, plus adding a third hormone—GnRH (gonadotropin-releasing hormone). Dr. Pike believes that use of such a pill could cut breast cancer risk in half.

How to Test Such Products?

“But how can we test this in our litigation prone era?” he asked. “The pharmaceutical companies are not interested in contraception because of the risk of lawsuits over side effects.”

One answer, he said, is to go ahead and make the product but not test it formally for breast cancer prevention.

“You make it for contraception, but if it does this other thing [prevention], well, that’s good, but we’re not going to talk about it,” he said. “We can’t spend $100 million on every one of these therapies and take 10 or 15 years to prove each one. We have to believe that the biology of the breast, as we understand it, tells us what is going to work.”