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BLOG: June 2008 CAT scan cancer riskIt was January 2001 when a Time magazine article cited the experts saying that parents shouldn't "panic" over then recent news reports of computerized axial tomography (CAT, or CT) putting their children at the increased risk of falling pray to cancer. In the context, one of the two studies breaking the news (Brenner et all.) was quoted, estimating that out of 1.6 million children who were getting CAT scans to the head and abdomen each year, about 1,500 will
eventually die Apparently, 1500 lives a year was considered by the experts to be an acceptable price to pay for the benefit of so many others. But is it all that plain and simple in this sad calculation? Another study from that time (Donnelly et al.) was quoted as pointing out that one of the biggest risk factors was that too many CAT scans were exposing children to adult-dose radiation, often unnecessary, since dose of radiation delivered by CAT-scan machine can be reduced up to 50% by a simple adjustment. Unnecessary...Remember this word, because it is to become the center point of the subject of CAT scan cancer risk. Now, fasten your seat belt and take your time-machine seven and a half years ahead, to June 2008. It is again the Time magazine, the same subject of CT scan radiation risk, and now another recent study led, again, by the same Dr. Brenner, director of the Center for Radiological Research at Columbia University Medical Center. In the meantime, the volume of CT scans performed in the U.S. rose to exceed 62 million a year. According to study's estimate, up to 1/3 of theses scans are unnecessary. This includes estimated over 1 million unnecessary CAT scans performed on children. If we apply the 2001 study ratio, this translates into 1,000 unnecessary cancer deaths from children's CT scan exposure alone, per year. In fact, a new FDA estimate for children CT scan cancer risk is 1 in 500, which doubles this figure: up to 2000 unnecessary cancer deaths per year caused by childhood CT-scan exposure. For adults, the FDA estimates the risk of dying from CAT scan radiation induced cancer to 1 in 2000 (for one-time dose of 10 mSv). With up to 20 million unnecessary CT scans each year, it translates into 10,000 unnecessary cancer deaths per year. The FDA estimates are based on the rate of increase in fatal
cancers in population of about 25,000
Japanese atomic bomb survivors, who were exposed to an average
radiation dose between 5 mSv and 20 mSv,
with relatively few of them as high as
50 mSv (mSv=millisievert, How does this level of radiation compares to the average CT scan radiation exposure? This question is answered by another recent study on 1243 randomly selected patients (Ballard), which has found out that average patient in the study had received 45 mSv of radiation from medical-imaging procedures, most of it from CAT scans. Put plainly, those poor Hiroshima and Nagasaki atomic bomb survivors had better chances not to die from radiation-induced cancer than an average U.S. patient using CT scan imaging. Here's a partial list of typical doses of radiation from various medical-imaging procedures (data source: Health Physics Society).
These are the typical exposures; actual exposures vary, sometimes significantly, with the machine and settings for X-ray and CAT scan, and both, the amount of radioactive (nuclear) material used and patient metabolism, with the nuclear medicine scans. In comparison, average yearly exposure to the natural background radiation is around 3 mSv (although it can vary significantly). In Bullard's study, 12% of the patients have been exposed to radiation in excess of 100 mSv. And the FDA's 1 in 2000 extra fatal cancer risk estimate due to additional radiation, as you recall, is based on a single 10 mSv average exposure. If the FDA estimate is anywhere close to correct, radiation doses delivered by most of diagnostic imaging procedures cannot be considered harmless, or negligible. Arguably, the risk estimates are still hypothetical, since it takes long time, often decades, from such an exposure to the actual onset of a disease, and the overall circumstance is not identical for the atomic bomb survivor in Japan, versus average patient over here. However, with the U.S. population significantly more exposed to a number of other carcinogens, nearly identical exposure to radiation is likely to result in more, not fewer cancers than in Japan. According to another recent study (Einstein et al., JAMA, July 2007), a 64-slice CT angiography scan will cause cancer in 1 in 143 women scanned at age of 20, and 1 in 284 women scanned at age of 40. The risk for men in these same age groups is roughly 4-5 times lower, due to higher radiation dose required to penetrate woman's breast tissue (21.4 vs. 15.2 mSv), combined with its high sensitivity. In the study, the highest cancer-risk organ with this particular CT scan were the lungs for general population, and breasts for younger women. CAT scan is an important diagnostic tool whose benefits, when properly used, justify acceptance of its risks. No one disputes this. What Dr. Brenner, Dr. Ozner and others are pointing out is that serious health risks
associated with radiation exposure or those with less threatening diseases, for any possible "reason". And that there is an epidemic of this type of CAT scan use. Aggressive marketing combined with unawareness of the risks associated with its use resulted in millions of unnecessary CT scan uses. Quite frequently, medical professionals recommend having CAT scan annually, "just to be safe", or expose a patient to more CT scans than is really needed. As Dr. Ozner points out, separate radiation exposures build up to your total exposure, accordingly increasing your risk of adverse health effects. These include - but not limit to - leukemia and cancers of the breast, lungs, and thyroid. He also emphasizes that FDA never approved CT scan for use on asymptomatic patients. Yet, the government agency, whose job is to oversee and regulate medical services, who claims its mission to be protecting the wellbeing of American public, idly stands by as The American College of Radiology, American Heart Association and other major medical organizations are expressing, for years, their concerns in regard to the overuse and abuse of CT scans. Not that the FDA is not keeping busy. Just this month, it sent out 25 warning letters to mostly Internet-based companies for selling products "fraudulently claiming to prevent and cure cancer". There is no adverse effects, let alone deaths, reported as a result of this activity. The agency is primarily concerned that the misleading statements used by these companies could deter some people from seeking proper treatment for cancer. While the FDA's definition of "proper cancer treatment" may be a subject for discussion, there is no question that medical services related to a disease as serious as cancer should be officially monitored. What doesn't add up is why is this apparently minor, even harmless activity more important to the FDA than correcting improper use of CT scans which, according to a number of reliable indicators, is likely taking thousands of lives already, and will cause many more thousands of unnecessary deaths in the years to come? YOUR BODY ┆ HEALTH RECIPE ┆ NUTRITION ┆ TOXINS ┆ SYMPTOMS |
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