Experts debate connection between CT and cancer

Clinical studies examining the potential of CT exposure to cause cancer are under way, but it could be years or even a decade until the results are known. Even then, they may be inconclusive, say expert presenters at the ISCT symposium on MDCT.

Dr. Andrew J. Einstein, an assistant professor of clinical medicine in radiology at Columbia University, examined the current basis for concerns about radiation exposure from CT, noting that none of the research used to support these cautionary arguments involve CT radiation exposure itself. Instead they are drawn from studies examining survivors of the atomic bombing of Hiroshima, accidents involving nuclear power plant workers, and exposure of children to radiation in utero.

A half dozen clinical studies are now enrolling hundreds of thousands of patients in Canada, the U.K., Australia, Israel, Sweden, and France with the goal of looking specifically at whether CT is a cause of cancer. But the studies, one of which involves pediatric patients, will take many years to complete. And there is no guarantee the results will be definitive.

“But it is still important that we do such studies because each additional study provides us with new information and a more complete picture of the issues that we are dealing with,” Einstein said.

In the meantime, the CT community and public will be left with only circumstantial data to make or break the connection between CT exams and cancer, a prospect that concerns Cynthia H. McCollough, Ph.D., director of the CT Clinical Innovation Center at Mayo Clinic College of Medicine.

Some patients are making bad decisions about their healthcare because of their unjustified fear of CT radiation, McCollough said, promulgated by a flawed base of research data. Despite 60 years of studying the Hiroshima data, for example, no definitive conclusions have yet been made about the cancer risk at doses commonly encountered during CT studies.

“When people say we just don't know what's happening, I disagree,” she said. “We know that it is not a big effect . If it is an effect at all, it is a really small effect.”

McCollough has a simple solution to the debate over radiation dose and CT, as it relates to deciding whether to schedule an exam.

“If the CT is needed, do it,” she said. “And if it's not needed, don't do it.”