by Ellen Leopold
Dormant since the 1980s, public fear of radiation now seems to be on the rise again. There is no longer any dispute about radiation’s carcinogenic effects. We have known for almost a century that radiation can damage genetic material and that its impact can be lasting and cumulative. From atomic witnesses (Hiroshima survivors and Americans living downwind of nuclear test sites in the 1950s), we have learned that radioactive fallout is linked to elevated rates of leukemia, breast, thyroid, and other cancers. All of these “man-made” cancers are tied to low doses of radiation, comparable to those used in medicine. But most scientists now agree that there is no dose low enough to be considered truly safe, no “threshold” of exposure below which radiation becomes harmless.
Yet radiation remains deeply enmeshed in the practice of American cancer treatment. In the form of ionizing rays and radioactive isotopes, atomic energy is integral to both diagnosis and treatment, used both to reveal malignancies and to control or destroy them. No one seems unduly alarmed by the multiplicity and compounding risks of these exposures. Few physicians ever bring them to the attention of their patients. Their silence on the subject reflects an almost unqualified conviction that the benefits of medical technology outweigh their risks. The prospect—or reality—of disease today will almost always crowd out any consideration of adverse consequences down the road.
Our unexamined tolerance for radiation risk is nothing new. Until the 1960s, chest x-rays were routinely used in annual screening for tuberculosis. In 1950, the medical establishment screened an estimated 15,000,000 Americans. Only one case of TB was revealed for every 1,000 chest x-rays taken. Eventually replaced by a skin test for tuberculosis, chest x-rays are still widely used in the diagnosis and monitoring of medical conditions, including emphysema, pneumonia, and heart failure as well as lung cancer.
But now this warhorse of exploratory testing has finally begun to show a darker side. The minimal dose of radiation it delivers might turn out not to be low enough. Recent evidence suggests that exposure to chest x-rays among women carrying the BRCA1/2 mutations increases their risk of breast cancer. Furthermore, as growing tissue is more at risk, the timing of exposure is critical. For those exposed under the age of 20, the increase in risk may be quite significant1.
The idea that low levels of radiation might be more hazardous than suspected magnifies the perils of another alarming trend—the explosive growth of computed tomography (CT) scans. This technology, which provides enhanced images, involves radiation exposures that far exceed those linked to traditional x-rays. A CT scan of the chest exposes a patient to doses up to 80 times higher than those linked to a single chest x-ray. Most CT procedures, in fact, reach levels that override the maximum allowable annual doses recommended by the National Council on Radiation Protection. And yet we take the safety of this technology for granted, submitting to procedures our physicians recommend, just as we consented to annual chest x-rays for almost half a century.
A 2007 article in the New England Journal of Medicine2 reported that 62 million CT scans were performed in the United States in 2006, a huge increase on the 3 million carried out in 1980. Some researchers estimate that up to one-third of them may have been medically unnecessary, which amounted to 20 million Americans undergoing unnecessary exposures. Such exposures are expected to account for up to 2 percent of all cancers diagnosed in the future—almost 30,000 new cases annually.3
But high as it is, this forecast includes only cancers associated with diagnostic tests, not those that might be linked to radiotherapies. Adding the latter to the total will push up the numbers. We have known since 1990 that the heavy doses of radiation once used to treat some childhood cancers pre-dispose survivors to another primary cancer years later. Young girls with Hodgkin’s disease, for instance, treated with radiation extending to the neck, chest, and axilla, have a higher risk for breast cancer as young adults. Some scatter-shot x-ray therapies have, over time, given way to more tightly focused procedures. But these gains in radiation control are offset by the much greater reach of radiotherapies across the board. Between 1974 and 1990, the number of new cancer patients receiving radiation treatment rose by 60 percent, and the number of radiation oncology facilities grew by almost 30 percent. By 2007, 800,000 Americans were undergoing some form of radiotherapy. How this correlates with improvements in survival, if any, or with the incidence of later cancers, remains to be discovered.
Given the multiple exposures to radiation throughout our lives in tests and treatments (not to mention the multiple involuntary exposures to radioactive toxins in the environment—in radon, cosmic rays, chemical solvents, coal ash, etc.), isn’t it time to impose some discipline on our vulnerability? Wouldn’t it be useful to keep a running tally of all the exposures we now consent to at our dentist’s and doctor’s offices and, increasingly, in shopping malls across the country? With something like a credit card, we could, in theory, keep track of all measurable exposures over a lifetime, acknowledging the cumulative impact of radiation on human biology and the need for continuity of care. A “radiation audit” would enrich the conversation between patients and physicians, bringing a more meaningful discussion of informed consent to every medical decision. It would also bring to the fore the question of acceptable alternatives, encouraging the substitution, wherever feasible, of newer and safer technologies such as MRIs and, for adults, ultrasound imaging. And, eventually, it might even help to forge a new awareness of patient-centered health care, transforming life histories into catalysts for change.
1 Nadine Andrieu, Douglas F. Easton, Jenny Chang-Claude, et al., “Effect of Chest X-Rays on the Risk of Breast Cancer Among BRCA1/2 Mutation Carriers in the International BRCA1/2 Carrier Cohort Study,” Journal of Clinical Oncology, 26 June 2006.
2 David J. Brenner and Eric J. Hall, “Computed Tomography: An Increasing Source of Radiation Exposure,” New England Journal of Medicine, Volume 357 (2007): 2277–2284.
Ellen Leopold contributes frequently to The Source. She is the author ofUnder the Radar: Cancer and the Cold War (Rutgers University Press, 2009) $25.95.