Fatal cancer deaths from CT scans half of previous estimates

A recent article regarding the incidence of cancer caused by CT scans was published in the Annals of Internal Medicine (1). The American College of Radiology has already published its own response (2). This topic is sure to attract the attention of the media and concerned patients who have recently weathered a similar storm regarding mammography.

All concerned parties should know that this article does not report an increase in the estimated rate of cancer caused by CT scans. In fact, it reports the opposite. However, it reports an increase in the number of cancers cased by the 3-fold increase in the number of CT scans done in the US since 1993. The projection of about 29,000 fatal and non-fatal cancers cased by about 70 million CT scans translates to about a 1 in 2400 chance of getting cancer from a CT scan, taking all patients together. However, the odds changed to about 1 in 2000 when the authors removed from the denominator patients who died (or were projected to die) within 5 years of the scan, before any radiation-induced cancer could develop, and patients with cancer at the time of the scan. The FDA estimated the odds of getting a fatal cancer to be 1 in 2000 (3), using cruder methods. Assuming a 50% cancer fatality rate, the new projections actually show the risk of fatal cancer from CT scans is half of what was previously thought.

A second article (4) will rightly cause even more alarm. This report analyzed the actual radiation doses delivered by four CT centers in the San Francisco area. These doses were both variable between centers and higher than assumed to be normal across the country. Thus, the calculated cancer risks were higher for these patients than in the other theoretical article, and these outlying data are the ones quoted by the media (5). Wake up, imaging centers! This article calls upon you to assure your scans are done with the minimum of radiation exposure to your patients.

Radiologists around the world are already striving to reduce the amount of radiation exposure for all types of CT scans and other methods that use ionizing radiation (6, 7). Alternative modalities are recommended whenver possible to achieve the same purposes (8). Each time a CT is planned, physicians must weigh the risk of inducing cancer against the potential benefit of the scan. Non-radiologists must not forget that CT scanners represent and unquestionalbly beneficial technology that has helped avoid exploratory surgery, provided guided interventional procedures to avoid other types of surgery, offered early diagnosis of disease to allow earlier and more effective treatment, and saved countless lives.

1. Original article http://tinyurl.com/yef4svl
2. ACR response http://tinyurl.com/ydqs338
3. FDA article http://tinyurl.com/m8cvxa
4. Second original article http://tinyurl.com/yevb6mt
5. WSJ article http://tinyurl.com/y9eko3b
6. Image Gently in pediatrics http://tinyurl.com/yagxrtv
7. Image Gently expansion http://tinyurl.com/y9f34d5
8. ACR appropriateness criteria http://tinyurl.com/ybcwvxr