CT scan radiations associated with increased risk for thyroid cancer and leukaemia

Globally use of computed tomographic (CT) scans has increased for diagnosing diseases. Although the use of computed tomography increases diagnostic accuracy the ionizing radiations from CT scans may increase the risk of cancer.

Researchers at Taipei Medical University, Taipei, Taiwan examined the association between medical radiation from CT scans and the risk of thyroid cancer, lymphoma, and non-Hodgkin lymphoma (NHL) in adults. They have found that exposure to radiation from CT scans is associated with higher risks of developing thyroid cancer and leukaemia. The new study has been published in JNCI Cancer Spectrum.

Researchers here conducted a study from a National Health Insurance dataset in Taiwan between 2000 and 2013. The study followed 22,853 thyroid cancer, 13,040 leukaemia, and 20,157 non-Hodgkin lymphoma cases. Researchers consulted data from the National Health Insurance program to study demographic and medical information on disease diagnoses, procedures, and drug prescriptions, and the enrollment profiles of all patients. Patients were excluded if they were under 25 years at the time of the cancer diagnosis, had less than three years of follow-up before cancer diagnosis, or had a history of cancer before the year 2000.

Results showed that patients who developed thyroid cancer and leukaemia had a significantly higher likelihood of having received CT scans. In studies that combined patients across age groups, exposure to medical CT scans was not associated with increased risk for non-Hodgkin lymphoma. However, in patients between 36 and 45 years of age, there was a three-fold increased risk of non-Hodgkin lymphoma associated with CT scans. In older patients, the association between exposure to CT scans and non-Hodgkin lymphoma was not evident.

Researchers concluded that patients receiving CT scans had in general marked increases in the risk of developing thyroid cancer and leukaemia, especially in female patients and patients younger than 45.

"Our study found that CT scans are associated with an increased risk of thyroid cancer and leukaemia in adults in all ages and with non-Hodgkin lymphoma in young adults," said Yu-Hsuan Joni Shao, one of the paper's authors. "The risk is stronger in patients who have higher cumulative doses from multiple scans. The increased numbers of people undergoing CT scans have become a public health issue."