LETTER
The Breast Cancer Screening Controversy Continues
Anthony B. Miller
1 May 1993 | Volume 118 Issue 9 | Pages 746-749
Dr. Miller responds: Dr. Kopans and Dr. Logan-Young and her colleagues make several erroneous statements. Centers were chosen for the National Breast Screening Study for their expertise in mammography. Expertise in screening was not available because there was no screening program in operation in Canada at the time. Thus, the radiologists, radiographers, and nurse-examiners learned to deal with the problems of screening on the job. We simply did not have the resources to send radiologists and technologists to Rochester, New York, or indeed anywhere else for training. We documented good sensitivity and specificity of both screening modalities [1, 2] and also demonstrated with the help of external reviewers that as mammography in North America in the 1980s improved, so did NBSS mammography [3]. The study reports document the extent to which we found early cancers as a result of using mammography.
Dr. Logan-Young misinterpreted the role she was invited to fulfill in the study. She was asked to join the Policy Advisory Group, not to act as reference radiologist. We were not prepared to send mammograms out of the country, but we were willing to have her review mammograms in Toronto, an opportunity that Dr. Feig took later. Dr. Sickles did not resign from the Policy Advisory Group. His role ceased when the Policy Advisory Group as a whole disbanded with the completion of our 7-year report.
Dr. Kopans continues to commit errors despite having them repeatedly pointed out to him. First, only 5.1% of all NBSS mammograms were produced in the first 2 years of screening, the period during which the reviewers regard some initial films to be unsatisfactory [4]. Second, when we reported on false-negative results in the study [5], we indicated those cancers that might have been detected 1 year before, not 1 to 5 years before, as well as how many cancers might not have been imaged because of technical factors.
Dr. Kopans also refers to the use of mammography in the control arms of the study. This was not contamination. Most of the mammograms were used for diagnostic purposes, as was anticipated, as mammography has been available for these purposes throughout Canada for two decades.
It is now recognized that no study has found evidence of benefit from mammography screening in women 40 to 49 years of age in the first 8 years after initiation of screening. The NBSS, which used two-view mammography given annually in addition to skilled physical examination, found many good-prognosis cancers early with good survival. The early detection of these cancers did not affect breast cancer mortality, and it seems very likely that finding similar cancers even earlier with more modern mammography will not have an effect either. Thus, there is no basis for recommending mammography screening in younger women.
1. Baines CJ, McFarlane DV, Miller AB, and collaborating radiologists. Sensitivity and specificity of first screen mammography in 15 NBSS centres. J Can Assoc Rad. 1988; 39:273-6.
2. Baines CJ, Miller AB, Bassett AA. Physical examination; evaluation of its role as a single screening modality in the Canadian National Breast Screening Study. Cancer. 1989; 63:160-6.
3. Baines CJ, Miller AB, Kopans DB, Moskowitz M, Sanders DE, Sickles CA, et al. Canadian National Breast Screening Study: assessment of technical quality by external review. AJR. 1990; 155:743-7.
4. Miller AB, Baines CJ, Sickles EA. Canadian National Breast Screening Study (Letter). AJR. 1990; 155:1133-4.
5. Baines CJ, McFarlane DV, Miller AB. The role of the reference radiologist: estimates of inter-observer agreement and potential delay in cancer detection in the National Breast Screening Study. Invest Radiol. 1990; 25:971-6.
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