Cancer risk is low for repeated lung CT scans for cystic fibrosis patients

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The cumulative risk of radiation-induced cancer from repeated lung CT scans for patients with cystic fibrosis is relatively small, less than 0.5 percent, according to the Nov. 15 issue of the American Journal of Respiratory and Critical Care Medicine.

Amy Berrington de González of the department of epidemiology at Johns Hopkins Bloomberg School of Public Health in Baltimore, and colleagues, said that CT is being considered as a tool for routine monitoring of lung damage in people with cystic fibrosis. The researchers set out to investigate the recent concern that has been raised about the associated risk of radiation-induced cancer.

The researchers estimated the risk of radiation-induced cancer from lung CT for patients with cystic fibrosis, assuming annual monitoring starting at age 2 years.

They reported that radiation risk models were used to estimate the excess risk of radiation-induced cancer for the organs that receive measurable doses from lung CT. Two scenarios were considered: median survival to age 36 years (approximate current median survival); and median survival to age 50 years (projected median survival by 2030).

Based on their results, de González and colleagues estimated the risk of radiation-induced cancer from annual lung CT was 0.02 percent for males and 0.07 percent for females assuming median survival to age 36 years. The estimated risks increased to 0.08 percent for males and 0.46 percent for females assuming median survival increases to age 50 years, the report said. The risks are higher for females because of the risk of radiation-induced breast cancer (50 percent of total risk) and higher risk of thyroid cancer.

Despite their findings, the researchers concluded that routine monitoring should not be recommended until there is a demonstrated benefit that will outweigh these risks.