Jewish World Review Feb. 26, 2002 /14 Adar, 5762

The continuing controversy regarding screening mammography

By Robert A. Wascher, M.D., F.A.C.S. -- I HAVE previously reported on the controversial findings of a recent Danish report on the value of screening mammography (Lancet, October 20, 2001). Briefly, the authors of that review analyzed the major clinical mammography studies completed within the last 20 years. They concluded, based upon statistical analysis of these previous studies, that there was no scientific evidence that screening mammography reduces the risk of death due to breast cancer in the general population. This paper set off a firestorm of debate around the world, with some experts very nearly labeling the Lancet paper's authors heretics. The impact of this paper upon the lay public was equally momentous, leading many women to confront their physicians for clarification.

As I have said before, it is important to understand that the conclusions of the Lancet paper were not based upon any new research that contradicted the previous research studies' findings. (The few large clinical trials that have been done to date concluded that screening mammography, at least among women older than 60, reduces the risk of death due to breast cancer by 20-30%.) Rather, the Lancet paper's authors retrospectively re-evaluated the methods and conclusions of the earlier mammography research trials, and concluded that the design of these trials, and the analysis of the resulting data, was flawed.

Thus, the Lancet paper concludes that the prior mammography trials cannot be used to confirm the general belief that mammography reduces the general public's risk of dying from breast cancer. This is a bit like analyzing all of the available data suggesting that there is a giant black hole at the center of our galaxy, and concluding that the evidence for such a finding is not solid enough to accept it as fact. This does not in any way prove that there is NOT a black hole in the center of the Milky Way galaxy. It just means that the analyst does not accept the evidence as being sufficient for proof.

Now, the National Cancer Institute (NCI) has stepped into the fray. A new consensus statement has just been released by the NCI following a review of the Lancet paper and the previous mammography studies, and following consultations with international experts on breast cancer and mammography. Based upon consideration of all facets of the issue, the NCI has formally recommended that women 40 and older should undergo routine screening mammography every 1 to 2 years. Women with an increased risk of breast cancer (including women with a family history of breast cancer, or with certain pre-malignant changes noted in their breast tissue following a biopsy) should seek additional recommendations from their physician prior to considering mammography before age 40. The NCI has also committed itself to closely monitoring the accumulating data on screening mammography from ongoing studies, and to funding additional studies in this area.

While the studies of the 1980s may indeed have their flaws, the overwhelming majority of physicians who care for breast cancer patients continue to believe that the benefits of screening mammography outweigh the risks when applied to women according to current NCI recommendations.

We know that there has been some improvement in the mortality rate due to breast cancer over the past decade after many decades of unchanged statistics. We also know that breast cancers have been diagnosed at an earlier stage, on the whole, since screening mammography became widespread in the United States and Western Europe. We also know that the risk of breast cancer recurrence and death is intimately proportional to the stage of the disease when it is first diagnosed and treated.

Although such empirical observations may not be fully validated by flawed earlier studies, such observations still stand on their own merits. We also know that more women are able to save their breasts more often because mammography has identified their disease when their tumors are still quite small.

However, even the NCI's latest firm pronouncements on this controversial subject will not idle all of the speculation and debate regarding the importance of mammography. There are a number of experts who argue that breast cancer has already become a systemic (body-wide) disease before it can be detected by mammography, and that even more sensitive diagnostic tools are necessary.

I have no argument with such observations. However, at the present time, screening mammography is the best screening tool that we have for the early detection of breast cancer in the general population. Even though 10 to 15% of breast cancers will not be apparent on mammography, there is nothing better available to replace it right now.

Bottom line: until a more sensitive and accurate test comes along, or until a large multicenter clinical trial shows absolutely no benefit to mammography in relation to its risks, you should follow the NCI's current recommendations.

JWR contributor Dr. Robert A. Wascher is a senior research fellow in molecular & surgical oncology at the John Wayne Cancer Institute in Santa Monica, CA. Comment by clicking here.


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© 2002, Dr. Robert A. Wascher