No Proof X-ray Radiation Causes Cancer | News | Loyola Medicine
Thursday, February 4, 2016

No Proof that X-ray Radiation Causes Cancer, according to Loyola Medicine Radiation Oncologist

MAYWOOD, Il. -  The widespread belief that radiation from X rays, CT scans and other medical imaging can cause cancer is based on an unproven, decades-old theoretical model, according to a study published in the American Journal of Clinical Oncology.

The model, known as linear no-threshold (LNT), is used to estimate cancer risks from low-dose radiation such as medical imaging. But risk estimates based on this model “are only theoretical and, as yet, have never been conclusively demonstrated by empirical evidence,” corresponding author James Welsh, MD and colleagues write. Use of the LNT model drives unfounded fears and  “excessive expenditures on putative but unneeded and wasteful safety measures.”

Dr. Welsh is a Loyola University Medical Center radiation oncologist and a professor in the Department of Radiation Oncology of Loyola University Chicago Stritch School of Medicine.

The LNT model dissuades many physicians from using appropriate imaging techniques and “discourages many in the public from getting proper and needed imaging, all in the name of avoiding any radiation exposure,” Dr. Welsh and colleagues write.

The authors reexamined the original studies, dating back more than 70 years, which led to adoption of the LNT model. This reappraisal found that the data reported in those studies do not actually support the LNT model.

In the LNT model, the well-established cancer-causing effects of high doses of radiation are extended downward in a straight line to very low doses. The LNT model assumes there is no safe dose of radiation, no matter how small. However, the human body has evolved the ability to repair damage from low-dose radiation that naturally occurs in the environment.

The LNT model dates to studies, conducted in the 1940s, of fruit flies exposed to various doses of radiation. The scientists who conducted those studies concluded there is no safe level of radiation, thus giving rise to the LNT model that is used to this day. But their conclusion was unwarranted because their experiments had not been done at truly low doses. A study exposing fruit flies to low-dose radiation wasn’t conducted until 2009, and this study did not support the LNT model.

Studies of atomic bomb survivors and other epidemiological studies of human populations have never conclusively demonstrated that low-dose radiation exposure can cause cancer.

Any claim that low-dose radiation from medical imaging procedures is known to cause cancer “should be vigorously challenged, because it serves to alarm and perhaps harm, rather than educate,” Dr. Welsh and colleagues write.

The authors conclude the LNT model “should finally and decisively be abandoned.”

The study is titled “The birth of the illegitimate linear no-threshold model – an invalid paradigm for estimating risk following low-dose radiation exposure.”

In addition to Dr. Welsh, co-authors are Jeffry Siegel, PhD, president and CEO of Nuclear Physics Enterprises (first author); Charles Pennington of NAC International and Bill Sacks, MD, PhD, emeritus medical officer in the FDA Center for Devices and Radiological Health.

About Loyola Medicine and Trinity Health

Loyola Medicine, a member of Trinity Health, is a quaternary care system based in the western suburbs of Chicago that includes Loyola University Medical Center (LUMC), Gottlieb Memorial Hospital, MacNeal Hospital and convenient locations offering primary and specialty care services from 1,877 physicians throughout Cook, Will and DuPage counties. LUMC is a 547-licensed-bed hospital in Maywood 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. Having delivered compassionate care for over 50 years, Loyola also trains the next generation of caregivers through its teaching affiliation with Loyola University Chicago’s Stritch School of Medicine and Marcella Niehoff School of Nursing. Gottlieb is a 247-licensed-bed community hospital in Melrose Park 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 in Berwyn with advanced inpatient and outpatient medical, surgical and psychiatric services, advanced diagnostics and treatments. MacNeal has a 12-bed acute rehabilitation unit, a 25-bed inpatient skilled nursing facility, and a 68-bed behavioral health program and community clinics. MacNeal has provided quality, patient-centered care to the near west suburbs since 1919.

Trinity Health is one of the largest multi-institutional Catholic healthcare systems in the nation, serving diverse communities that include more than 30 million people across 22 states. Trinity Health includes 94 hospitals, as well as 109 continuing care locations that include PACE programs, 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 $18.3 billion and assets of $26.2 billion, the organization returns $1.1 billion to its communities annually in the form of charity care and other community benefit programs. Trinity employs about 133,000 colleagues, including 7,800 employed physicians and clinicians. Committed to those who are poor and underserved in its communities, Trinity 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.