Healthy Skepticism Library item: 7039

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Publication type: news

Editorial .
A Big Drop in Breast Cancer
The New York Times 2006 Dec 16
http://www.nytimes.com/2006/12/16/opinion/16sat1.html?_r=1&oref=slogin

Abstract:

The sharp drop in breast cancer rates reported this week is astonishingly good news. It is the first major reduction in the incidence of a malignancy that strikes more than 200,000 American women every year – and kills some 40,000 annually.

Researchers from the M. D. Anderson Cancer Center in Houston and other institutions reported that the incidence of all types of breast cancer fell a stunning 7 percent in 2003 – the latest year for which statistics are available – from the year before. This was the first such decline after persistent rises for several decades and a leveling off from 1998 to 2002. The researchers estimate that 14,000 fewer women were diagnosed with breast cancer in 2003 than in the year before.

The most plausible explanation is that women by the millions abandoned or sharply cut back their use of hormone therapy. For many years hormones – which have been widely used to treat the symptoms of menopause – had also been hyped by the pharmaceutical industry as an elixir to ward off the ravages of aging. Overly enthusiastic doctors also championed hormone therapy as a way to prevent or mitigate heart disease, Alzheimer’s, severe depression and urinary incontinence – none of which turned out to be true.

But in mid-2002, a study of the effects of hormones on thousands of women had to be halted after it became clear that prolonged use of a popular hormone combination caused an increase in breast cancer, heart attacks, strokes and blood clots.

Women abandoned the hormone pills in droves, and almost immediately, the incidence of breast cancer began to fall. As Gina Kolata reported in yesterday’s Times, rates of the most common form of breast cancer – tumors that are fueled by estrogen – dropped a startling 15 percent from August 2002 to December 2003.

The researchers hypothesize that tiny tumors in the breast, when deprived of the hormones that fueled them, stopped growing or at least grew more slowly, leaving them too small to be detected on mammograms.
It is also possible that, with their hormones cut off, some tumors shrank or even disappeared. Other factors, like a slight dip in mammography screening to detect tumors and use of drugs that are known or thought to slow breast cancer, might have played a small role in reducing the numbers, but they were deemed too inconsequential to explain the results.

The great unknown is what will happen in the future. If tumor growth was simply slowed, not stopped, the tumors may become detectable as time goes on. But hormone therapy has continued to decline, so the drop in breast cancer is apt to continue. A study in California found that a sharp decrease in breast cancer incidence in 2003 was followed by a slower but continued drop in 2004, a harbinger, perhaps. of what national statistics will show next year.

Further analyses will be needed to identify all possible reasons for the decline of breast cancer incidences. If the hypothesis holds up that the drop in hormone use is the main cause, as seems likely, it should persuade even more women to curb their use except when absolutely necessary. Meanwhile, breast cancer incidence will remain high, underscoring the need for more ways to prevent this dreaded disease.