Better Detection Could End Screening Debate

June 1, 1995

TORONTO, Canada--The benefits of annual mammography screening for women aged 50 and over are undisputed, but experts are still polarized over whether the screening procedure is worthwhile for women aged 40 to 49.

TORONTO, Canada--The benefits of annual mammography screeningfor women aged 50 and over are undisputed, but experts are stillpolarized over whether the screening procedure is worthwhile forwomen aged 40 to 49.

Prominent specialists debated the issue at a controversy sessionat the annual meeting of the American Association for Cancer Research(AACR), with one researcher suggesting that development of teststo improve interpretation of the ambiguous mammograms often seenin younger women could someday render the discussion moot.

Possible Risks of Screening

Making the case against mammography screening for women in their40s was Karla Kerlikowske, MD, a primary care physician and epidemiologistat the University of California, San Francisco.

In her analysis of 13 international breast cancer studies (JAMA,January 11, 1995), Dr. Kerlikowske found that regular mammographyscreening did not significantly decrease breast cancer mortalityamong women aged 40 to 49.

She informs her patients in this age group that there is no proofthat mammography decreases breast cancer deaths and that thereare risks to undergoing screening, such as the possibility ofinconclusive tests and the risk of unnecessary diagnostic teststhat cause anxiety and discomfort.

"For a 40-year-old woman who elects annual screening for10 years, I tell her that she has a 25% chance of having an abnormalmammogram during those 10 years. There is a 23% chance of a falsepositive, and a 6% to 7% chance of biopsy. But the chance of cancerbeing detected is only 1.5%," she said.

Because of the large numbers of ambiguous, inconclusive mammogramsand false positives, many women must undergo additional expensivetests. "It's estimated that thousands of unnecessary biopsiesare performed each year. And all of this causes distress in patients,"she said.

Dr. Kerlikowske said that up to 40% of women who have abnormalmammograms will have anxiety for 3 months. The small group thatneeds to undergo biopsy may have anxiety for up to 18 months.And in that group, the anxiety may persist even after the womanlearns that she has nothing to worry about.

She is also concerned about the false reassurance resulting froma false-negative mammogram. She fears that a woman who detectsa lump after a normal mammogram may not seek further screening.

Virginia Ernster, PhD, of the University of California, San Francisco,who moderated the debate, is herself a woman in the disputed agegroup. She has elected not to have annual mammograms.

There is nothing magical about age 50, she said. She suggestedthat regular screening could start earlier or later, dependingon menopausal status, but "physicians may find it easierto ask a woman her age than her menopausal status."

The Case for Screening

Coming out firmly in favor of early screening to aid detectionwas Edward A. Sickles, MD, a radiologist at the University ofCalifornia, San Francisco. Recent reports suggest an 8% drop inbreast cancer mortality for Caucasian women 40 to 49 years old,he said, and mammography may be partly responsible.

As for the existing data suggesting that screening is not beneficialin this age group, he contends that the studies may be statisticallyinvalid for younger women because breast cancer mortality is solow in this age range.

He added that the most recently published compilation of internationalbreast cancer studies, using, he said, more recent data than thosepresented by Dr. Kerlikowske, shows a statistically significant24% reduction in breast cancer mortality for mammography screeningof women aged 40 to 49 (Smart CR et al: Cancer, April, 1995).

Dr. Sickles noted that mammography may be discouraged in thisage group because the denser breast tissue of younger women canobscure tumors and make the procedure less accurate. But he thinksthis argument is negated by improvements in mammography techniquesthat allow physicians to "see more in the images," hesaid.

To Dr. Dutzu Rosner, of the State University of New York at Buffalo,the answer to the question of mammography in the 40s is reallyimproved adjunctive imaging techniques that would help physiciansinterpret ambiguous mammograms in this age group.

Dr. Rosner and his team are studying a radioactive isotope attachedto a monoclonal antibody that zeros in on breast tumors. Dr. Rosner,who presented his research at the conference, believes that thismethod could be an important back-up to ambiguous mammograms.

To date, in the studies at Buffalo, radioimmunodetection has proven83% to 100% accurate in predicting which ambiguous mammogramsare not breast cancers, depending on the type of monoclonal antibodyused.

He cautioned that the results are very preliminary, with only19 women studied so far. However, he said, these results are similarto those reported in January in a European study, which foundno false-positive tests in 31 women studied.

A paper describing the Buffalo study has been accepted by CancerInvestigation, he said, and is scheduled for publication in thefall of this year.