X-Rays and Health

* Whereas dosage, from any medical agent which is a proven carcinogen and mutagen, should be measured, recorded, and kept as low as technically possible, consistent with obtaining its medical and dental benefit;

* Whereas nuclear workers have their exposures to radiation routinely measured, even though they often accumulate less exposure than non-cancer medical patients;

* THEREFORE, medical and dental patients have the right (a) to know their radiation exposures from x-ray imaging procedures and to possess a reliable dose-record, and (b) to know that the medical and dental communities are actively seeking the most effective ways to reduce dosage during x-ray imaging procedures,

XaHP Document 104 lists several techniques which can reduce x-ray dosage, while still obtaining high-quality images. Patients who are willing to ask about such matters as peak kilovoltage, filtration, distance from the x-ray focal point to the patient, etc., will have additional ways to discern which x-ray practitioners in their area are more likely to give lower doses than others.

And what if your HMO or other health insurer does not permit a choice of x-ray practitioners? What then? Whenever customers (you) cannot take your business elsewhere, "market forces" are very weak.

That is why the Patients' Right-to-Know Policy Statement is so needed. (If no local group has the Statement yet, XaHP can supply you. The "bottom line" is printed below.) A rapidly and constantly growing number of signatures on the Policy Statement provides a way, locally and nationally, to focus the attention of HMOs, hospitals, radiologists, other physicians, and the various accrediting organizations, upon the Policy Statement's goal: Lower x-ray doses per x-ray procedure.

There is no mystery about how to reduce doses, technically. What is lacking is leadership. If just a few thousand American radiologists would openly endorse the goal, their leadership (in our opinion) could reduce the average dose-level administered by other radiologists virtually overnight. Other kinds of x-ray practitioners would follow suit.

The leadership of radiologists, which we encourage, would provide the fastest, most efficient, and lowest-cost way to get the job done.

" ... Therefore, medical and dental patients have the right (a) to know their radiation exposures from x-ray imaging procedures and to possess a reliable dose-record, and (b) to know that the medical and dental communities are actively seeking the most effective ways to reduce dosage during x-ray imaging procedures."

The Probability of Radiation Harm - Using the assumptions that the mean glandular dose to the breast per 2-view exam is 0.2 rad (0.2 centi-gray or cGy), that a woman starting at age 50 accumulates 15 mammograms, and that 3.7 is the incidence to mortality ratio, we estimated that the likelihood of a fatal mammogram-induced breast-cancer is roughly 1 chance in 500 (Gofman 1996: pp.180-81 for incidence, adjusted for fatality, pp.279-80).

But the upper limit of "permissible" dose per exam has been 0.6 rad. For individuals receiving 0.6 rad per exam, the dose and the risks would be three-fold higher. And the risks would also be variably higher for women who (unknown to them) have inherited certain genetic mutations (e.g., in the AT gene or in other DNA) which make x-ray-induced damage less likely to be correctly repaired.

Even so, it is reasonable to think that, from annual screening, your chance of not developing a mammogram-induced fatal breast cancer greatly exceeds the chance that you will.

How likely are false-positive mammograms in the USA? In 1998, the New England Journal of Medicine published a study, based on the HMO records of 4,319 women who received mammograms between 1983 and 1993 (Elmore 1998). The resulting estimates are (p.1092): For women having mammographies at age 50 or older, the cumulative risk of false-positives after five screening mammograms is 24%, and after ten exams, 47%. For younger women (age 40-49), the risks are, respectively, 30% and 56%. Such studies have stimulated progress on computer-assisted interpretation of mammograms, aimed at reducing such very high rates.

The findings above were supported by a separate study published in the Journal of the National Cancer Institute (Christiansen 2000). This study looked additionally at how the false-positive rate varied with the number of breast-cancer risk factors a woman has. "By the ninth mammogram, the risk [of a false-positive result] can be as low as 5% for women with low-risk variables and as high as 100% for women with multiple high-risk factors."

The external pressure on women to have periodic mammograms has been intense. But considering the uncertainty that mammograms will deliver more personal benefit than harm, "Rational women can make the decision not to have a mammogram, and no one should castigate them for doing that," says Russell Harris, M.D., of the University of North Carolina Medical School and member of a National Cancer Institute advisory board (in Greider 2002, p.15).

June 2005 - For at least the past seven years I have been educating people about the risks of x-ray with the help of Dr. Gofman. Today, 29 June, the following was announced:

Panel Affirms Radiation Link to Cancer - By H. JOSEF HEBERT, Associated Press Writer

Even very low doses of radiation pose a risk of cancer over a person's lifetime, a National Academy of Sciences panel concluded Wednesday. It rejected some scientists' arguments that tiny doses are harmless or may in fact be beneficial.

The findings could influence the maximum radiation levels that are allowed at abandoned reactors and other nuclear sites. The conclusions also raise warnings about excessive exposure to radiation for medical purposes such as repeated whole-body CT scans.

"It is unlikely that there is a threshold (of radiation exposure) below which cancers are not induced," scientists said in the report.

While at low doses "the number of radiation-induced cancers will be small ... as the overall lifetime exposure increases, so does the risk," the experts said.

Scientists for years have debated how extremely low doses of radiation affect human health.

Pro-nuclear advocates, as well as some independent scientists, have maintained that the current risk models for low-level radiation has produced more stringent requirements than is necessary to protect public health.

It is an issue in determining decontamination requirements at abandoned reactors and at federal weapons sites.

The academy's panel stood by the "linear, no threshold" model that generally is the acceptable approach to radiation risk assessment. This approach assumes that the health risks from radiation exposure decline as the dose levels drop, but that each unit of radiation — no matter how small — is assumed to cause cancer.

"The scientific research base shows that there is no threshold of exposure below which low levels of ionized radiation can be demonstrated to be harmless or beneficial," said Richard R. Monson, the panel's chairman. He is a professor of epidemiology at Harvard's School of Public Health.

The panel said new and more extensive data developed over the past 15 years only strengthen the conclusions of the panel's last report, in 1990, on low-level radiation risks.

The scientists estimated that one out of 100 people exposed to 100 millisievert of radiation over a lifetime probably would develop solid cancer or leukemia, and that half of those cases would be fatal.

It also said that 42 additional cancers can be expected in the same group from other than low-level radiation sources.

A millisievert is a measurement of radiation energy deposited in a living tissue. People absorb about 3 millisievent of radiation annually from natural sources and 0.1 millisivert every time they get a chest X-ray.

The report noted that exposure from a whole body CT scan is about 10 millisievert, much higher than a normal X-ray. That raised concerns about the frequency of such medical diagnostics.

The report should not scare people away from nuclear medicine, said Dr. Henry Royal, a professor of radiology at Washington University in St. Louis. He said most often the benefits of such tests and treatments outweigh the risks.

But Royal also said that procedures such as CT scans should be used to deal with a specific medical problems and not part of annual medical screenings. "You should not be exposed to radiation for superficial reasons," Royal said in a telephone interview.

Some anti-nuclear advocates said the study reaffirms that stringent regulations are needed when cleaning up abandoned nuclear sites or considering health risks near nuclear power plants.

"The NAS panel puts to rest once and for all claims that low doses of radiation aren't dangerous ... nuclear advocates have been making this claim for years" said Daniel Hirsch, president of Committee to Bridge the Gap, a Los Angeles-based nuclear watchdog group.

Mitchell Singer, a spokesman for the Nuclear Energy Institute, the industry's lobbying arm, said the report "is a positive finding. It shows there is very little risk of exposure from low levels of radiation."

The academy is a private organization chartered by Congress to advise the government of scientific matters.

National Academy of Science: www.nationalacademies.org

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