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Guest column

Benign biopsy doesn't eliminate risk of breast cancer

By V. UPENDER RAO
Published September 26, 2005

Researchers from the Mayo Clinic in Rochester, Minn., published the results of a study they conducted that outlines the risk of developing breast cancer among women who had a benign diagnosis on their initial breast biopsy.

They categorized the benign diagnosis as follows:

--Nonproliferate epithelium, meaning normal breast tissue. The biopsy was likely undertaken because of an abnormal mammogram report. No excess risk of cancer during the next 10 to 15 years was found unless there is a strong family history of breast cancer among first-degree relatives (parents and siblings).

--Proliferative epithelium, meaning there is accelerated growth of a part of the breast as compared to the rest of the breast. An 83 percent relative risk of developing breast cancer in the next 10 to 15 years was noted with this finding if the initial biopsy was performed at or younger than age 40.

--Atypia, meaning abnormal appearance of breast epithelial cells compared with normal cells in the adjacent breast tissue. A fourfold increase of the probability of developing breast cancer was noted if atypia was in association with proliferative or rapidly growing epithelium.

These figures have a tremendous impact on women. Millions undergo mammography screening each year; 20 percent of those screened will undergo a biopsy within 10 years of getting their first mammogram. This number is likely to increase because, although the benefit of mammography screening is more definite among women age 50 and older, a number of organizations in the United States recommend initiating screening at age 40.

According to the National Center for Health Statistics, as of 2000, 70 percent of women age 40 and older had undergone mammography in the preceding two years. In the same year, 18-million mammograms were ordered through physician offices and 1.5-million through hospital outpatient departments.

The Mayo Clinic researchers chose to report "relative risk," which leads to a greater perception of risk as opposed to "absolute risk," which is more realistic and easily understood by most physicians and patients.

For instance, five of every 100 women in the U.S. population can expect a diagnosis of breast cancer in the next 15 years. Of 100 women with benign breast biopsy at or before age 40, six can be expected to develop breast cancer within the next 15 years. This is one more than the expected five per 100 women.

In terms of relative risk, this magnitude will be stated as 27 percent; in terms of absolute risk, it will be stated as 1 in 100 (one more than the expected five per 100).

The highest risk among patients with benign breast biopsy is for those who have atypia in combination with proliferative epithelium. Among 100 women with this combination, 19 can expect a diagnosis of cancer in the following 15 years as opposed to five of 100 women in the general population who have no known risk factors.

This analysis explains the vast difference in perception of risk when expressed in terms of relative risk rather than absolute risk. Most people understand words much better than numbers, and physicians are no exception. A typical medical school curriculum is not extensive enough to teach statistical and probability thinking and communicating risk in a realistic, easily understood manner.

Breast cancer is not a single disease. Many factors can lead to certain changes in the breast tissue that the pathologist might call breast cancer. Within this one entity, there can be 100 variations of potential for the cancer to be indolent, grow rapidly, spread, respond to certain treatments better than some others, to cause damage to and kill the patient. Therefore, assessing the risk based on pathology alone will probably be a thing of the past.

In the future, risk will likely be based on analysis of the molecular footprint of each cancer and comparing it with a library of footprints whose behavior and reproduction has been observed and confirmed.

In 2004 there were 10,000 medical articles published under the rubric of "risk." This is a ninefold or 900 percent increase compared with 1975. Obviously, risk and the risk of cancer, in this case, are on the minds of the American people. As things stand today, the tools on which risk calculation depends are evolving. Until more reliable methods become available, we must strive to communicate the risk in realistic, understandable and optimistic terms.

Framing is a statistical term. It is akin to "the glass being half full or half empty" philosophy. For instance, I might tell Mrs. X in the "negative frame" that her risk of developing cancer in the next 10 years is 10 percent; in the "positive frame," I might tell her that her chance of not developing cancer in the next 10 years is 90 percent!

--V. Upender Rao, MD, FACP, practices at the Cancer and Blood Disease Center in Lecanto.

[Last modified September 26, 2005, 01:18:19]