Canadian study clouds mammogram issue Do younger women who get mammograms yearly lower their risk of breast cancer?

May 08, 1992|By Jonathan Bor | Jonathan Bor,Staff Writer

As Mother's Day approaches, health organizations are once again gearing up to send mothers -- and daughters -- a powerful message about breast cancer. The message: Catch it early. Get a mammogram.

But this week, many younger women will be greeting this appeal with profound confusion and annoyance. News trickling out of a massive study of Canadian women has suggested that women in their 40s who get annual mammograms do nothing to lower their chances of dying of breast cancer.

"I've had calls today from patients who are reasonably hysterical," said Dr. Alex Munitz, chairman of radiology at the Greater Baltimore Medical Center and a vocal critic of the study.

In part, the consternation can be blamed on erroneous reports that said women under 50 in the study who got mammograms actually died at a faster rate than did those who weren't screened. With seven years of data, the study found that any differences in the death rates were statistically insignificant.

For all practical purposes, say scientists involved in the study, the death rates were the same.

Although the sentiment isn't unanimous, many physicians say the public shouldn't put too much stock in the early results out of Canada. The study, they say, may be too young to produce results that mean anything.

And while a half-dozen studies of mammography have reached conflicting conclusions, many doctors insist their own experiences as doctors leave them convinced that mammography saves the lives of young and old alike.

The research has touched a nerve because it appears to contradict the advice of the American Cancer Society and about 10 other health organizations -- advice that has permeated American society. Those groups recommend annual mammograms for women 50 and older, and screenings every year or two for women between the ages of 40 and 49.

The recommendation is based on the simple observation that breast cancer is often cured when a tumor is small and self-contained. Mammography, a technology using low-dose X-rays, can often capture those small tumors while they are still in that stage.

Once the cancer has spread to tissues outside the breast, however, the mortality rate soars.

So widely accepted are the recommendations that many states require insurance companies to cover mammography screenings, which cost about $60, for women over 40.

In Maryland, the law requires companies to cover mammograms every two years for women in their 40s and annually for older women. (The law does not apply to policies provided by employers that self-insure.)

Breast cancer among young women is less common than it is among older women, but it remains a serious concern. It is the leading cause of death among women 40-49, an age group marked by generally good health. This year, the Cancer Society estimates that 180,000 cases of breast cancer will be diagnosed across America -- 22 percent of them among women in their 40s. Seventy-eight percent of the cases will be in the over-50 group.

The furor revolves around the Canadian National Breast Screening Study, a study of 90,000 women that began in 1980 to evaluate the usefulness of screening women between the ages of 40 and 60 with X-ray technology.

Although researchers have yet to publish results, the study's principal investigator said seven years of data -- more recent statistics have yet to be evaluated -- show benefits for the older women but none for the younger.

"We're in for a long haul before it is absolutely certain that there is no benefit, but it's clear on a short-term basis that there is no benefit," said Dr. Anthony Miller, who directs the study. He is a professor of preventive medicine and biostatistics at the University of Toronto.

"At least the American Cancer Society should inform women that there is no guarantee they will have reduced the risk of breast cancer deaths if they have screening mammograms," Dr. Miller said. "I don't think public policy should be promoted on the basis of deceiving women."

Although the study is purely a statistical one, Dr. Miller said there may be reasons why younger women don't benefit from mammograms. One problem may be that some younger women get a particularly aggressive cancer.

Other cancer specialists have noted that many younger women have dense breast tissue that can hide a small tumor.

Biological differences aside, Sam Shapiro of the Johns Hopkins School of Hygiene and Public Health said it is probably impossible to draw conclusions at this point in the study. Even if it is true that annual mammograms save lives of younger women, he said, it is unlikely that the significant differences in death rates would show up only seven years into a study.

"The early years are not a good predictor of what you're going to end up with in terms of measuring the benefits of mammography," said Mr. Shapiro, an adviser to the Canadian study. "I'd say at about 10 or 11 years, you should have quite a good indication of what the picture would be in the long run.

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