The role of repeated PET/CT scans and additional risk factors in predicting cancer mortality among Ozyorsk residents

The article aims at assessing the impact of diagnostic radiation exposure from positron-emission computed tomography (PET/CT) examinations and other risk factors on cancer mortality among residents of the nuclear city of Ozyorsk, examined at the Chelyabinsk Regional Clinical Center of Oncology and Nuclear Medicine. Data on gender and age at exposure, the number of PET/CT examinations, total activity of the administered radiopharmaceuticals and radiation doses delivered to patients during PET/CT examinations, were retrospectively collected. Information on potential contact with occupational radiation exposure for Mayak PA workers was included in the study. The number of additional routine computed tomography examinations, performed outside the Center of Nuclear Medicine, and the related effective dose of diagnostic radiation were calculated. For cancer patients, information on the stage of malignancy, chemotherapy, and radiotherapy administered were collected. Information on vital status and cause of death was updated as of December 31, 2022. The impact of repeated PET/CT, taking into account other radiation and non-radiation risk factors, was assessed using multivariate regression analysis. It was found that repeated PET/CT examinations of cancer patients, resulting in a total cumulative radiation dose up to 400 mSv, were not associated with a negative survival prognosis over an average follow-up period of 3.5 years. The main non-radiation risk factors contributing to cancer mortality among the study cohort were age at exposure and the stage of malignancy.