Radiation burden from recurrent computed tomography examinations in patients treated with immunotherapy for malignant...

Computed tomography (CT) examination is among the imaging modalities burdened with a relatively high dose of ionizing radiation. Nowadays, CT is an integral part of modern medicine. In the field of oncology care, patients undergo repeated CT examinations for initial diagnosis, staging, and follow-up. However, we usually only have a rough idea of how high the radiation exposure these examinations actually represent for the patient. It is general agreement that received effective dose (ED) greater than 100 mSv represents a significantly higher risk of radiation-induced fatal malignancy over the course of the patient's life. In our study, we focused on the radiation burden that these recurrent CT scans represent for patients undergoing immunotherapy for metastatic malignant melanoma.

Our study had a retrospective design. Study group consisted of all patients treated with immunotherapy for metastatic malignant melanoma between 2016 and 2021. We included 54 patients with median age of 66 years, interquartile range (IQR) 15 years. We retrospectively calculated the EDs of their individual CT examinations (n=622) then calculated the cumulative dose (CED) for each patient.

Study subjects underwent median 8 CT examinations (IQR, 9 examinations), with a minimum 2 and a maximum 25 CT examinations. In 35 patients (64%) CED exceeded 100 mSv, in 17 (31%) subjects CED was over 200 mSv and in 11 (20%) was over 300 mSv. The highest achieved CED was 547.7 mSv.

We proved that recurrent CT scans performed for follow-up care are associated with a high CED. A CED higher than 100 mSv, is considered as significant for the risk of developing radiation-induced malignancy later in the patient's life. Although other factors such as age, gender or individual sensitivity must be taken into account, the high CED from such examinations should be considered, especially when creating follow-up care plans and recommendations.