As rates of diagnostic imaging in medicine have skyrocketed over the past 20 years, a major concern for public health officials is the possibility of radiation-induced malignancy. Collective radiation dose to the average American from medical imaging grew six-fold from 1990 to 2006, mostly due to growing use of 3D scanners with greater radiation exposure than traditional radiographs. CT scans alone, which account for half the public medical imaging dose, are estimated in some studies to be responsible for up to 2% of all cancers with 2007 rates of CT usage.
However, a recent study, published in Radiology by Dr. Pari V. Pandharipande and colleagues at Massachusetts General Hospital, suggests that such risks may be overstated. The team used CT radiation dose data to model effects of early versus delayed risks, life expectancy losses and lifetime mortality risks due to testicular cancer. They devised a Markov model to project outcomes for testicular cancer patients who undergo CT surveillance in the decade after orchiectomy, or removal of the testicle. Such a model accounts for mortality, disease incidence, and quality of life.
Based on the results of their analysis, the researchers suggested in one scenario that 33-year-old men with early-stage cancer who undergo regular CT surveillance have a higher mortality risk from testicular cancer over their lifetime compared with potential radiation-induced cancers. Because the testicular cancer risk was more immediate, however, the life expectancy loss attributable to testicular cancer was over three times greater than that attributable to radiation-induced cancers. These trends were similar in other scenarios analyzed.
What this suggests, according to Dr. Pandharipande, is that when considering diagnostic imaging, physicians must weight immediate health risks against the potential of future radiation-induced malignancy:
This must be considered when physicians make imaging decisions for their patients, because the timing of risks changes their relevance…Risks incurred later in life are not the same as those faced in the present. If you had to choose between the chance of incurring a serious risk now or later in life, most people would choose the latter.
This data illustrate the difficulty of applying population-based concerns, for example those about radiation-induced cancer, to clinical decision-making about an individual patient. Educating physicians about interpreting such data in the context of individual treatment decisions will certainly be necessary.
Pubmed Abstract of Journal Article: Patients with Testicular Cancer Undergoing CT Surveillance Demonstrate a Pitfall of Radiation-induced Cancer Risk Estimates: The Timing Paradox.