Increasing Number of CT and PET Scans Raise Cancer Risk Concerns

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A new research study reveals a striking increase in the number of CT and PET scans being performed, resulting in increased radiation exposure levels




Last week, I discussed new data regarding CT scans in children, and the potential increase in lifetime cancer risk associated with these scans.  This week, I will continue with this general theme by reviewing a new clinical study, published in the Journal of the American Medical Association, that documents the continuing rise in the number of medical imaging studies being performed, including computed tomography (CT) scans.  In view of this continuing increase in the number of medical imaging exams being performed, public health experts are concerned that cancer rates may also rise.

As I discuss in my bestselling book, A Cancer Prevention Guide for the Human Race, exposure to medical x-rays, and particularly exposure to radiation from CT scans, is an under-appreciated cancer risk factor.  Based upon conservative estimates, exposure to medical radiation is thought to cause approximately 2 percent of all new cancer cases, and most of this medical x-ray exposure comes from CT scans and positron emission tomography (PET) scans.

It is important to acknowledge that, when ordered and performed appropriately, CT scans, PET scans, and other medical imaging studies offer enormous potential benefits to patients and their doctors, and the benefits of medical imaging far outweigh the risks in such cases.  However, since the advent of CT scans and other forms of advanced medical imaging, many physicians have increasingly come to rely upon these imaging studies when other methods of clinical diagnosis that do not expose patients to large doses of ionizing radiation will work just as well.

In this new clinical study, the electronic medical records systems of 6 large integrated health care systems in the United States were analyzed.  In this very large study, between 1 and 2 million patient records were reviewed every year between 1996 and 2010.  All patient-members enrolled in the following health care organizations during this 15-year period were evaluated:Group Health Cooperative in Washington State; Kaiser Permanente in Colorado, Georgia, Hawaii, Oregon, and Washington; and the Marshfield Clinic and Security Health Plan in Wisconsin.

The focus of this study was on Health Maintenance Organizations (HMOs), because these organizations typically have very robust utilization management systems that are designed to monitor for, and prevent, wasteful or inappropriate medical studies, including unnecessary medical imaging exams.  Given that the use of advanced medical imaging studies has skyrocketed in the fee-for-service world in recent years, the authors of this new study sought to assess trends in the use of advanced medical imaging studies among HMOs, specifically.

During the 15-year study period, the patients of these 6 HMOs underwent 31 million medical imaging exams, equal to an average of 1.2 imaging tests per year for every patient-member.  More than one-third of these medical imaging exams were advanced medical imaging studies (CT scans, MRI scans, PET scans, and ultrasound scans).  When measured on an annual basis during the 15 year duration of this study, CT scan exams increased by 8 percent per year, while MRI scans increased by 10 percent per year.  PET scans, which are typically combined with CT scans, increased by a whopping 57 percent per year from 2004 through 2010.  (Ultrasound scans, which, like MRI scans, do not expose patients to ionizing radiation, increased by 4 percent per year.)

Of particular interest to me, as a cancer prevention expert was the finding that the increased use of CT scans resulted in a per capita doubling of radiation exposure doses among the patient-members of these 6 HMOs.  Moreover, the proportion of patient-members who received high and very high medical radiation doses also doubled during the course of this study, reflecting the increased use of high-energy medical imaging studies, including, primarily, CT scans and CT-PET scans.  Indeed, by 2010, 7 percent of these HMO patient-members received medical imaging studies that placed them within the “high annual radiation exposure” category (> 20-50 millisieverts, or mSv), while 4 percent of patients received “very high annual radiation exposure” doses of medical radiation (> 50 mSv).

Once again, it is important to stress that advanced medical imaging is a very powerful tool that can provide physicians with essential diagnostic information for many of their patients.  However, experts in the fields of Radiology and Public Health have become very concerned, in recent years, regarding the questionable indications for advanced imaging scans in many cases.  Indeed, there is the sense that these powerful diagnostic scans are too easily and too quickly ordered in many cases, and without compelling clinical justification.  Therefore, it behooves both patients and their physicians to ask a simple but very important question:  Does the likely benefit of undergoing a CT scan or CT-PET scan outweigh the possible associated risks?  If the answer to this question is no, then such scans should not be performed.

At this time, 8.2 percent of Americans are unemployed.  According to the Bureau of Labor Statistics, however, the unemployment rate for veterans who served on active duty between September 2001 and December 2011 is now more than 12 percent.  A new website, Veterans in Healthcare, seeks to connect veterans with potential employers.  If you are a veteran who works in the healthcare field, or if you are an employer who is looking for physicians, advanced practice professionals, nurses, corpsmen/medics, or other healthcare professionals, then please take a look at Veterans in Healthcare.

For a groundbreaking overview of cancer risks, and evidence-based strategies to reduce your risk of developing cancer, order your copy of my bestselling book, “A Cancer Prevention Guide for the Human Race,” from AmazonBarnes & NobleBooks-A-MillionVroman’s Bookstore, and other fine bookstores!

Within one week of publication, A Cancer Prevention Guide for the Human Race was ranked #6 among all cancer-related books on the “Top 100 Bestseller’s List” for Kindle e-books. Within three months of publication, A Cancer Prevention Guide for the Human Race was the #1 book on the Amazon.comTop 100 New Book Releases in Cancer” list.

Disclaimer:  As always, my advice to readers is to seek the advice of your physician before making any significant changes in medications, diet, or level of physical activity


Dr. Wascher is an oncologic surgeon, professor of surgery, cancer researcher, oncology consultant, and a widely published author


I and the staff of Weekly Health Update would again like to take this opportunity to thank the more than 100,000 health-conscious people from around the world who visit this premier global health information website every month.  (More than 1.3 million pages of high-quality medical research findings were served to the worldwide audience of health-conscious people who visited Weekly Health Update in 2011!)  As always, we enjoy receiving your stimulating feedback and questions, and I will continue to try and personally answer as many of your inquiries as I possibly can.


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