Radiation, CT & Cancer: Is There Really A Link? | Loyola Medicine
Tuesday, July 7, 2015

Loyola radiation oncologist questions studies that show link between X-ray radiation, CT scans and cancer

MAYWOOD, IL – In recent years, there has been widespread media coverage of studies purporting to show that radiation from X-rays, CT scans and other medical imaging causes cancer.

But such studies have serious flaws, including their reliance on an unproven statistical model, according to a recent article in the journal Technology in Cancer Research & Treatment. Corresponding author is Loyola University Medical Center radiation oncologist James Welsh, MS, MD.

“Although radiation is known to cause cancer at high doses and high-dose rates, no data have ever unequivocally demonstrated the induction of cancer following exposure to low doses and dose rates,” Dr. Welsh and co-author Jeffry Siegel, PhD, write.

Studies that have found a cancer link to medical imaging typically employ a model called “linear no-threshold” (LNT). In LNT, the well-established cancer-causing effects of high doses of radiation are simply extrapolated downward in a straight line to low doses. The LNT model assumes there is no safe dose of radiation, no matter how small.

But although LNT is used by regulators around the world, the model “is of questionable validity, utility and applicability for estimation of cancer risks,” Drs. Welsh and Siegel write.
Contrary to the LNT model, there is compelling evidence that the human body has evolved the ability to repair damage from low-dose radiation. For example, the mutation rate caused by low-dose background radiation in the environment is 2.5 million times lower than the rate of spontaneous mutations in the body. So even if the LNT model were true, the small increase in mutations caused by low-dose radiation from medical imaging would be unlikely to overwhelm the body’s defenses.

Studies purporting to find a cancer link to medical imaging radiation have other flaws besides the questionable LNT model. For example, two recent studies suggested possible increased cancer risks from low-radiation doses associated with pediatric CT scans. But these cancers likely are due to the medical conditions that prompted the CT scans, and have nothing to do with the radiation exposure, Drs. Welsh and Siegel write.

While many people focus on the purported risks of radiation in medical imaging, “the more significant and actual risks associated with not undergoing an imaging procedure or undergoing a more invasive exploratory surgery are generally being ignored in both the scientific literature and the popular media,” Drs. Welsh and Siegel write.

Dr. Welsh is a professor in the Department of Radiation Oncology of Loyola University Chicago Stritch School of Medicine. Dr.  Siegel is president and CEO of Nuclear Physics Enterprises in Marlton, N.J.

Their paper is titled: “Does imaging technology cause cancer? Debunking the linear no-threshold model of radiation carcinogenesis.”

 

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Loyola Medicine is a quaternary care system based in the western suburbs of Chicago that includes Loyola University Medical Center (LUMC) in Maywood, Gottlieb Memorial Hospital (GMH) in Melrose Park, MacNeal Hospital in Berwyn and convenient locations offering primary and specialty care services from more than 1,772 physicians throughout Cook, Will and DuPage counties. LUMC is a 547-licensed-bed hospital that includes the William G. and Mary A. Ryan Center for Heart & Vascular Medicine, the Cardinal Bernardin Cancer Center, a Level 1 trauma center, Illinois's largest burn center, a certified comprehensive stroke center and a children’s hospital. The medical center campus is also home to Loyola University Chicago Stritch School of Medicine, Loyola University Chicago Marcella Niehoff School of Nursing and the Loyola Center for Fitness. GMH is a 247-licensed-bed community hospital with 150 physician offices, an adult day care program, the Gottlieb Center for Fitness, the Loyola Center for Metabolic Surgery and Bariatric Care and the Loyola Cancer Care & Research at the Marjorie G. Weinberg Cancer Center at Melrose Park. MacNeal Hospital is a 374-bed teaching hospital with advanced inpatient and outpatient medical, surgical and psychiatric services, advanced diagnostics and treatments in a convenient community setting. Loyola Medicine is a member of Trinity Health, one of the nation’s largest health systems with 94 hospitals in 22 states.

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Trinity Health is one of the largest multi-institutional Catholic health care delivery systems in the nation, serving diverse communities that include more than 30 million people across 22 states. Trinity Health includes 93 hospitals, as well as 122 continuing care programs that include PACE, senior living facilities, and home care and hospice services. Its continuing care programs provide nearly 2.5 million visits annually. Based in Livonia, Mich., and with annual operating revenues of $17.6 billion and assets of $23.4 billion, the organization returns $1.1 billion to its communities annually in the form of charity care and other community benefit programs. Trinity Health employs about 131,000 colleagues, including 7,500 employed physicians and clinicians. Committed to those who are poor and underserved in its communities, Trinity Health is known for its focus on the country's aging population. As a single, unified ministry, the organization is the innovator of Senior Emergency Departments, the largest not-for-profit provider of home health care services — ranked by number of visits — in the nation, as well as the nation’s leading provider of PACE (Program of All Inclusive Care for the Elderly) based on the number of available programs. For more information, visit www.trinity-health.org. You can also follow @TrinityHealthMI on Twitter.