Lancet Study Shows Cancer Risk Increases After Childhood CT Studies

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In a joint study of the long-term health outcomes of pediatric cancer patients dating back as far as 1985, radiation from diagnostic imaging scans nearly tripled children’s risks for leukemia and brain tumors, according to a study published in The Lancet. Even excluding from its assessment CT studies that were conducted as a course of cancer treatment, researchers observed an increased risk for cancers in their follow-up. Given these findings of associated risk, researchers are advocating for the use of alternative diagnostic methods that include non-ionizing radiation whenever possible in dealing with pediatric populations. “Although CT scans are very useful clinically, potential cancer risks exist from associated ionising radiation, in particular for children who are more radiosensitive than adults,” the study found. The relative risk of leukemia for “patients who received a cumulative dose of at least 30 MGY” was three in 18, and the relative risk of brain cancer for patients who received a cumulative dose of 50 MGY was two in 82. “Because these cancers are relatively rare, the cumulative absolute risks are small,” researchers reported. “In the 10 years after the first scan for patients younger than 10 years, one excess case of leukaemia and one excess case of brain tumour per 10 000 head CT scans is estimated to occur.” Out of concern that parents would read into the study reasons to keep their children from getting necessary imaging tests, the American College of Radiology published a statement on the Lancet study today: “Children who get CT scans are doing so because of an immediate and significant health condition,” read the ACR statement. “These are not screening exams given to the general population of children. “The authors stressed that the absolute lifetime cancer risks found in the study are very small compared with the lifetime risk of developing cancer in the general population, and are likely small compared with the benefits of a clinically justified scan…The use of appropriateness criteria to maximize the benefit relative to risk has been a major emphasis of the ACR. The authors correctly note that CT scanners from the period studied (1989-2003) used radiation doses much higher than those of today. Current protocols also allow for use of much lower dose than the study period. “As the authors highlight, providers are far more aware of the potential risks involved than in years past and largely are proceeding as if low doses of radiation cause harm.” The ACR response also points out that initiatives like Image Gently and Image Wisely have helped to lower pediatric dosing standards in the time since the research was conducted. The study was funded jointly by the US National Cancer Institute and UK Department of Health.