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John W. Gofman, M.D., Ph.D., Professor Emeritus,
Molecular and Cell Biology, Univ. Calif. Berkeley
and Egan O'Connor, Exec. Director, CNR and XaHP.
XaHP Document 108, October 2000
XaHP: The X-rays and Health Project.
An educational project of the
Committee for Nuclear Responsibility.
Part 1. The Non-Mammographic X-Ray Exams
There is no conflict whatsoever between a woman taking her annual mammograms and the SAME WOMAN working hard to reduce the x-ray doses received during other kinds of x-ray imaging procedures. A mammographic exam typically delivers about 0.2 dose-unit ("rad") to each breast. By contrast, a single CT exam of the chest is said to give each breast about 5 rads (Gray 1998a, p.63) --- or 25 times more x-ray exposure. Common cardiac angiographies "often" give skin doses approaching 100 rads, according to UNSCEAR (1993, p.233, Para.71). If true, this may mean that segments of the breast "often" receive over 50 rads during such procedures.
We praise the fact that typical dosage per mammogram is more than 10-fold lower than it was in the early 1970s (Gofman 1999, p.18). XaHP's goal is to achieve the same kind of attention to dose-reduction in all x-ray imaging --- especially with CT scans and fluoroscopy, which currently account for the most patient exposure.
A current TV ad, promoting General Electric's Senograph 2000-D digital mammography system, includes the following acknowledgment that every reduction in dose is desirable: The system results in "fewer re-takes, which means less discomfort and less radiation."
Part 2. Discarding the Principle of Informed Consent?
Several famous and widely accepted studies show that exposure to x-rays is a cause of breast cancer, even when the cumulative dose is the result of minimal doses per exposure (references in Gofman 1999, pp.523-524; the newest confirmation is in Doody 2000). Each new dose adds risk, because a single x-ray photon, acting alone, is capable of causing unrepairable, permanent damage to DNA and chromosomes --- including carcinogenic mutations (Gofman 1990, Chapters 18-21; NRPB 1995, pp.58-75).
The principle of informed consent in medicine would be turned upside down, if anyone tries to keep women unaware of such evidence, so that women will more readily consent to annual mammograms. Even though the motive is good, would it not be trickery to obtain consent by deliberately blocking valid information? In our opinion, women are entitled to know the full range of responsible opinion about the benefits, the risks, and the many uncertainties of mammography (for example, Wright 1995, + Elmore 1998, + Woolf 1999, + Miller 2000, + Christiansen 2000).
Part 3. The Forgotten Men? A Serious Moral Downside
The reason for reducing x-ray dosage per x-ray procedure is the fact that x-rays are a proven cause of human cancers. If mammography enthusiasts were to try to obscure this fact, in order to help women accept mammography, there would be a serious moral downside: All the men would be hurt. Males as well as females would suffer from not reducing x-ray dose per x-ray procedure. For both genders, reduced x-ray dose per x-ray procedure guarantees fewer cases of xray-induced cancers in the future. And powerful new evidence indicates that reduced x-ray dose per x-ray procedure would also mean many fewer cases of xray-induced coronary heart disease in the future (Gofman 1999, Chapters 40-46).
Part 4. A Mysterious Hole in the War on Cancer
If there is a war on cancer, but no group or agency is devoted to reducing exposure to a proven cause of every major type of cancer --- namely, x-rays --- then the decision to neglect x-rays really causes the future xray-induced cancers (and heart attacks) which could have been prevented. This logic creates the moral obligation to succeed at what is demonstrably feasible: Obtaining all the benefits of medical and dental x-rays, at lower doses per procedure. An imaginary conflict, between this goal and mammography, would be tragic for nearly everyone.
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(1) "The capacity of ionizing radiation to produce breast cancer has been repeatedly confirmed." *
(2) "The strongest evidence for a particular initiating factor in breast cancer is that for irradiation ... Evidence that other carcinogens initiate breast cancer development is extremely limited." **
Both quotations above come from the medical text "Cancer of the Breast, Fourth Edition" 1995, edited by William L. Donegan and John S. Spratt (published by W.B. Saunders).
* From Chapter 8 (at p.131), "Epidemiology and Etiology," by Professor John S. Spratt, M.D., FACS (Brown Cancer Center, University of Louisville School of Medicine, KY), Prof. William L. Donegan, M.D., FACS (Sinai Samaritan Medical Ctr., Milwaukee, WI), and Prof. Curtis P. Sigdestad, Ph.D. (Radiation Oncology Dept., Brown Cancer Center, Univ. of Louisville Sch. of Med., KY).
** From Chapter 9 (at p.143), "Prevention of Breast Cancer," by Richard R. Love, M.D. (Prof. of Human Oncology, Univ. of Wisconsin at Madison) and Polly A. Newcomb, Ph.D. (Asst. Professor, Dept. of Human Oncology, Univ. of Wisconsin Medical School at Madison).
- Christiansen 2000, Cindy L. et al. "Predicting the Cumulative Risk of False-Positive Mammograms," J. of the Natl Cancer Inst Vol.92, No.20: 1657-1666.
- Doody 2000, Michele M. et al. "Breast Cancer Mortality after Diagnostic Radiography: Findings from the U.S. Scoliosis Cohort," Spine Vol.25, No.16: 2052-2063.
- Elmore 1998, Joann G. et al. "Ten-Year Risk of False Positive Screening Mammograms and Clinical Breast Examinations," New England J. of Med. Vol.338, No.16: 1089-1096.
- Gofman 1990, John W. Radiation-Induced Cancer from Low-Dose Exposure: An Independent Analysis. 480 pages. ISBN 0-932682-89-8. San Francisco: Committee for Nuclear Responsibility Books.
- Gofman 1999, John W. Radiation from Medical Procedures in the Pathogenesis of Cancer and Ischemic Heart Disease: Dose-Response Studies with Physicians per 100,000 Population. 699 pages. ISBN 0-932682-97-9. San Francisco: Committee for Nuclear Responsibility Books.
- Gray 1998a, Joel E. "Lower Radiation Exposure Improves Patient Safety," in Diagnostic Imaging Vol.20, No.9: 61-64.
- NRPB 1995. National Radiological Protection Board (British Government). Risk of Radiation-Induced Cancer at Low Doses and Low Dose Rates for Radiation Protection Purposes. 77 pages. ISBN 0-85951-386-6. Documents of the NRPB, Vol.6, No.1. Chilton, Didcot: NRPB.
- UNSCEAR 1993, United Nations Scientific Committee on the Effects of Atomic Radiation. Sources and Effects of Ionizing Radiation: 1993 Report to the General Assembly, with Scientific Annexes. 922 pages. ISBN 92-1-142200-0. U.N. sales number E.94.IX.2.
- Miller 2000, Anthony B. et al. "Canadian National Breast Screening Study-2: 13-Year Results of a Randomized Trial in Women Aged 50-59 Years," J. of the Natl Cancer Inst Vol.92, No.18: 1490-1499.
- Woolf 1999, Steven H. "Differing Perspectives on Preventive Care Guidelines: A New Look at the Mammography Controversey," Amer. J. of Preventive Med. Vol.17, No.4: 260-268.
- Wright 1995 (July 1), Charles J. "Screening Mammography and Public Health Policy: The Need for Perspective," Lancet Vol.346: 29-32.
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"The American Cancer Society firmly believes that any risk, no matter how small, should be reduced as much as possible and that radiographic equipment should deliver the lowest dose of radiation consistent with producing an optimal diagnostic image."
--- From pg. 228, "Mammography 1982: A Statement of the American Cancer Society," approved by the ACS Medical and Scientific Committee and Board of Directors. In "CA - A Cancer Journal for Clinicians," Vol.32, No.4: 226-230. July/Aug. 1982.