When it Comes to Breast Cancer, a Girl Can’t be Too Barefoot and Pregnant—and Thin!

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Every year, in early December, I’m irresistibly drawn to Texas, and the annual San Antonio Breast Cancer Symposium (SABCS), where I gather with 9,000 others to learn what insights the past year has yielded about breast cancer causes, prevention and treatment. A joint effort of the American Association for Cancer Research, Baylor College of Medicine and the University of Texas Health Science Center, the SABCS is the largest scientific meeting in the world dedicated exclusively to breast cancer research. For me, the anticipation begins even before I arrive, spotting fellow advocates and oncologists I know at the airport.

Valerie Beral, an epidemiologist at the University of Oxford in England, opened this year’s conference with a plenary session on the causes and prevention of breast cancer. This was hardly new information, yet I found it compelling.

“Why,” Beral asked, “does breast cancer vary across the world so dramatically?” She noted that the cumulative incidence of breast cancer until age 70, by percentage of the population, is only about 1 percent in rural Africa and Asia. In contrast, in developed countries, the cumulative incidence is six- to sevenfold higher, with breast cancer affecting 6 percent of women by age 70. Furthermore, while the rates of new breast cancers have apparently stabilized in developed countries like the U.S., the rates are now rising steeply—just as they did here 30 to 40 years ago—in the crowded cities of the developing world.

If this trend continues—and there is no reason to believe it won’t before it, too, levels off—the one million cases of breast cancer diagnosed worldwide each year will double by 2040, she added. What could be responsible for these hugely escalating numbers?

The protective nature of early childbearing and breastfeeding is of course well known, as are the changing childbearing patterns that occur when women move to cities and leave rural life. In the 18th century, said Beral, Italian physician Bernardino Ramazzini referred to breast cancer as “an occupational disease of nuns,” observing that nuns in Verona suffered a sevenfold higher mortality from the disease.  “For over two centuries,” said Beral, “it was believed that a major cause of breast cancer was women not using their breasts for ‘natural purposes.’ ” Indeed, more recent research has shown that each pregnancy confers a 10 percent reduction in risk. “We are all nuns,” concluded Beral.

But the story turns out to be far more complicated than exposure to the protective hormones of early pregnancy and breastfeeding. Starting in the 1970s, according to Beral, with the rise of birth control and, later, with the tremendous rise in the use of postmenopausal hormones, a large part of the female population was being exposed to “exogenous” hormones—those not naturally occurring in the body. The revelation in 1991, from the Women’s Health Initiative study, that hormone replacement therapy (HRT) promoted breast cancer (as well as heart disease, stroke and some dementia), led to a massive drop in hormone use. This, in turn, Beral said, led to a major decrease in breast cancer incidence that was seen almost immediately in the United States, as well as in a dozen countries around the world that had similarly high rates of post-menopausal hormone use.

What does this tell us? ”Breast cancer incidence in developed countries would be more than halved if women had similar childbearing patterns to women in developing countries,” said Beral. The rest of the risk disparity between developed and developing countries can be accounted for by so-called “nutrition” factors, she said, noting that obesity, early menarche and alcohol consumption have all been associated with higher rates of breast cancer, and with breast cancer recurrence. (Later in the day we heard two studies that confirmed this association.) In fact, Beral said, statistical modeling shows that there would be 40,000 fewer breast cancer diagnoses each year in the U.S. if women were not obese and did not drink alcohol or use HRT.

Since it’s not likely that most women will be returning to villages to bear many children at a young age, Beral suggested that we need to develop a way, perhaps with a vaccine, to reduce breast cancer incidence by mimicking the protective effects of youthful, full-term pregnancy.

The advocates I spoke with were far from convinced. Having been down that risky road of hormonal protection already, we can be forgiven for our skepticism. What about other factors not discussed by Beral, like environmental risks or the endocrine disruptors we’re told act like estrogen?  There was, as there always is at this meeting, a lot to ponder.

Musa Mayer

www.AdvancedBC.org

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