Is There A Link Between CT Scans And Higher Cancer Rates?
Physicians reportedly obtain over 60 million computed tomography (CT) scans each year in the United States. However, a recent study in the New England Journal of Medicine (NEJM) suggests that CT scans may be linked to an increased risk of radiation exposure and cancer.
Citing evidence from epidemiologic studies, the authors of the NEJM article indicate that organ doses from a common CT study, consisting of two or three scans, may result in an increased risk of cancer.
“As compared with plain film radiography, CT involves much higher doses of radiation, resulting in a marked increase in radiation exposure in the population,” note the authors of the NEJM review article.
They concede that there are no currently published epidemiologic studies that look at cancer risks associated with CT scans. However, the authors of the NEJM article note that “applying organ-specific cancer incidence or mortality data” from long-term follow-up studies of atomic bomb survivors allows estimates of the link between radiation exposure from CT scans and cancer risk.
Citing reports from the literature, the authors of the NEJM review suggest that CT scans are overutilized and may be part of a defensive medicine approach. Robert Baron, DPM, echoes the study’s concern about defensive medicine.
“Unfortunately, this has developed largely due to our litigious society,” says Dr. Baron, a Professor and Chairman of the Department of Radiology at William M. Scholl College of Podiatric Medicine at Rosalind Franklin University. “These exams are also ordered without much regard to the radiation exposure received by patients. Exposure can be minimized with proper workup and scanning limited to a very specific area.”
Daniel Evans, DPM, says there is “no question” that ionizing radiation can lead to cell changes, which may precipitate the development of cancer. However, no longitudinal study has demonstrated a direct connection between CT exposure and the development of cancer, and he notes that the NEJM review extrapolated gamma radiation from Hiroshima and Nagasaki to other types of radiation such as X-ray. “The level and extent of the biological effects may vary,” says Dr. Evans.
Dr. Evans, the Assistant Chairman of the Department of Radiology at the William M. Scholl College of Podiatric Medicine, also points out that the NEJM review looked at CT scans done on the abdomen and chest, which would give more ionizing radiation to internal organs, lymphatic tissue and gonadal tissue. There is no data specific to the lower extremity.
Podiatrists most commonly use CT scans for conditions such as Lisfranc fractures, calcaneal fractures, coalitions, suspected osteomyelitis, Charcot neuroarthropathy and ankle fractures, according to Drs. Evans and Baron. Dr. Evans notes that podiatric scans are performed in areas that have a low incidence for the development of cancer. He says podiatric studies are rarely done repeatedly on the same patient, which minimizes the cumulative dosing to patients.
Reducing Radiation Risk And Addressing Patient Concerns
How can physicians reduce the risks associated with radiation? Dr. Evans suggests DPMs not be cavalier when ordering CT scans and should exercise caution when scanning kids. Dr. Baron says advances in magnetic resonance imaging (MRI) are making that modality the gold standard for imaging various pathological conditions that were once the province of CT. He says the drawback to MRI remains the cost. Another option is ultrasound although the application is somewhat more limited, according to Dr. Baron.
How can one address patient concerns about CT scans? Dr. Baron says he would explain the benefit/risk ratio but says he would not force the issue. Dr. Evans says one should take patient concerns seriously, informing patients there is a potential risk with any type of ionizing radiation.