Survival and radiation risk in patients obtaining more than six CT examinations during one year

During a review of the current practice for computer tomography (CT) in 2005 at the Department of Radiology, Aarhus University Hospital, we observed 300 patients with more than six CT examinations during one year. They comprised 8% of the patients and accounted for 27% of all examinations. These patients needed further analysis.

The 300 patients were analyzed concerning age, type of diseases indicating multiple CTs and the CT protocols used. The effective dose and risk of low dose radiation was estimated and survival of the patients after >1.5 year was analyzed.

A total of 289 patients had malignancies, the most frequent being lung cancer, bladder cancer and colon cancer. A total of 4.3% of the patients with malignancies were < or =40 year old, 13.3% were 41-50 years old and 62.7% 51-70 years old. The highest average number of CT examinations was observed in patients with sarcomas (11.2 examinations per patient). Eleven patients (aged 15-77 years) had traumatic lesions. Their number of examinations varied from 7 to 20. The total radiation dose for all 300 patients was 21.42 Sv, which may imply induction of a fatal cancer in one of the patients. However, only 102 patients survived their disease.

A total of 198 patients had serious disease and were not alive 1.5 years after the examinations. The multiple CT examinations were necessary to monitor their treatment. For the surviving 102 patients the use of CT contributed to an optimal therapy, but the examinations implied a risk for radiation induced malignancies.