Timing mammogram to menstrual cycle

October 07, 1997|By Judy Foreman | Judy Foreman,BOSTON GLOBE

This summer, a Canadian study of nearly 7,000 women came to a startling conclusion: that a mammogram done during the second half of the menstrual cycle is twice as likely to miss a lurking cancer as one taken during the first half.

For now, these researchers think this applies only to women who use or have used hormones such as birth control pills. And because there is so little research on the question, the finding could turn out to be a statistical fluke.

Still, the idea is intriguing -- as is the suggestion from a handful of other studies that there may also be an optimal time in the cycle for a woman to have breast cancer surgery.

The hypothesis that a woman's cycle may affect diagnosis or treatment of breast cancer raises "pretty interesting questions," says Dr. Jay Harris, chief of radiation oncology at Brigham and Women's Hospital and the Dana-Farber Cancer Institute, both in Boston.

In fact, there's still no evidence that timing chemotherapy or radiation to a woman's cycle affects the outcome, says Dr. Ken Cowan of the National Cancer Institute. But there are three major studies now under way to see whether the odds of survival increase if a woman has breast cancer surgery at a particular point.

And there are already enough reasons, some specialists say, to recommend that women maximize their chances of an accurate mammogram by having it during the first half of their menstrual cycle, after a period is over.

"Although one never wants to take action on the basis of only one study," says Dr. Cornelia J. Baines, the University of Toronto epidemiologist who led the Canadian study, having a mammogram in the first half, or follicular phase, of the cycle "can't do harm and may do good."

Baines also believes that the apparent increased likelihood of missing a cancer in the second half of the cycle may partially explain why it has proved so hard to document a clear benefit of mammograms for women aged 40 to 49.

Nobody knows why mammograms would be harder to read during the second, or luteal, half of the cycle, she says, though it may be because of increased fluid and cellular activity in the breasts. In general, she notes, it's harder to read mammograms in women with denser breasts, but it is not clear whether breast density -- as opposed to swelling -- increases late in the cycle.

Breasts are softer early in the cycle, says Dr. Dan Kopans of the breast imaging division at Massachusetts General Hospital, which means there is less pain when they are compressed for the X-ray. And better compression yields more accurate mammograms.

However, many centers do not routinely schedule mammograms according to a woman's cycle.

"It's very difficult to schedule screening mammograms with your cycle because they are booked in advance," adds Dr. Norman Sadowsky, director of the Faulkner-Sagoff Imaging and Diagnostic Center in Boston. But it is "very reasonable" to try to schedule them in the first half of cycle because of the improved compression.

Research with a different type of test, magnetic resonance imaging, supports the idea that the second week of the cycle may be best for mammograms and breast self-exams -- and the fourth week the worst, he says.

A far dicier question is whether to schedule surgery to coincide with a presumed optimal time in the cycle. Even if proven desirable, it could be tricky to do because women with suspected cancer often have several surgeries over several weeks -- a biopsy to see if a lump is cancerous and later, removal of the lump or breast and some lymph nodes.

Still, the studies are intriguing -- and contradictory.

Nearly a decade ago, Dr. William Hrushesky, an oncologist at the Stratton V.A. Medical Center in Albany, N.Y., kicked off the debate with a study in mice that suggested the chances of a cure were doubled or tripled if breast tumors were removed around the time of ovulation.

Other studies suggest there may be an advantage to surgery in the second half of the cycle. The theoretical reason for this -- and it's far from proven -- is that in the first half of the cycle, the hormone estrogen, which can drive some breast cancers, is "unopposed" in a woman's body. In the second half of the cycle, estrogen is balanced by the hormone progesterone.

So until better answers are in, what should a woman do?

Talk it over with your doctor, of course, and perhaps bear in mind the view of breast cancer guru Dr. Susan Love, adjunct professor at the UCLA School of Medicine. She says, through a spokeswoman, that she sees "no harm from scheduling these patients [for surgery] during the early luteal phase."

Pub Date: 10/07/97

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