Patients who undergo CT scans may
be prone to develop brain tumors
later in life, according to a
Dutch study

Study: CT use possibly linked to higher risk for brain tumors

July 20, 2018
by John R. Fischer, Senior Reporter
Going for a CT scan? Be careful. You might get brain cancer.

Such a query has been the subject of debate among numerous healthcare professionals worldwide and is once again in the spotlight following the release of a new study by Dutch researchers who suggest that exposure to radiation during CT imaging may place a person at higher risk of developing brain tumors later in life.

“Our work is an important addition to the evidence of cancer risks at low radiation doses, supporting extrapolations from the A-bomb survivors and other populations exposed to higher levels,” Michael Hauptmann of the department of epidemiology and biostatistics at the Netherlands Cancer Institute and an author of the study, told HCB News. “This knowledge informs regulation of exposures to patients and personnel in hospitals, nuclear workers, airline personnel and other exposed groups. It also directly supports radiation protection standards in medical imaging, and proposes their implementation wherever this is not yet the case.”

The use of CT scans has risen significantly over the last two decades due to their enhanced diagnostic capabilities. Performing these exams, however, exposes patients to greater amounts of radiation compared to other imaging modalities, a fact that has created cause for concern, particularly among children, who are more susceptible to radiation-related malignancies than adults and have more time to exhibit the effects of this possible risk.

In their study, researchers evaluated CT scans of 168,394 children examined between 1979 and 2012 to determine if such exposure led to the development of brain tumors or leukemia, the most common malignancies incurred from radioactivity in young adults and children. Dose-response relationships were also calculated based on observations of radiation dosage to the brain.

Overall cancer incidence was 1.5 times higher than expected, while increases in relative risk, based on all brain tumors combined as well as malignant and nonmalignant brain tumors separately, reached between two and four for the highest dose category. No association was found for leukemia, with bone marrow exhibiting low findings of radiation dosage.

Hauptmann warns that while significant, the results of the study should not dissuade patients from avoiding CT all together.

“The principles of radiation protection, justification of imaging and optimization of doses, should be followed everywhere according to the standards,” he said. “Then, the benefits should exceed the risks and forgoing a procedure could be dangerous. Absolute risks from low-dose radiation are much lower than other health risks we happily take every day.”

Echoing this sentiment is Marta Hernanz-Schulman, radiology vice chair for pediatrics and medical director of diagnostic imaging at Monroe Carell Jr. Children's Hospital at Vanderbilt.

“I agree with the authors that the results need to be interpreted with caution, as this pattern of excess cancer risk may be partly due to confounding by indication,” she said. “I also agree that CT scans are potentially life-saving. We believe in the principle of justification, that scans should be done only when indicated, that the radiation used should be child-sized, and that only the region indicated should be scanned.”

Though an important source of evidence for the impact of radiation dosage from CT, the study is limited by the incidence of brain tumors being higher in the cohort than in the general population, an indication that may partially have influenced the results of the study. In addition, CT is sometimes used to identify conditions associated with an increased tumor risk, which may account for why these children were referred for these exams in the first place.

Scans were collected from Dutch-based radiology departments of hospitals, the only facilities in the Netherlands where pediatric CT exams are performed. All departments were surveyed to determine eligibility and participation.

The study was published in the Journal of the National Cancer Institute.