Background: Recently, awareness of the cumulative radiation exposure for pediatric oncology patients has been increasing, together with increased survival rates and longer life expectancy. The aim of our study was to quantify the amount of ionising radiation from imaging modalities of pediatric oncology patients.

Methods: Eighty-eight patients who were diagnosed with childhood cancer and followed up for 5 years between 2004-2014 in our center were included in the study. Patients' medical fi les were reviewed retrospectively for imaging history in the first 5 years after diagnosis. Total estimated effective doses from radiologic imaging modalities were determined. Also, the basic demographic data, histologic type, stage, and outcomes of disease were collected for all patients.

Results: The individual total estimated effective doses ranged from 8.73 to 167 mSv, with a median of 62.92 mSv. Computed tomography was the greatest contributor of total effective doses. The doses ranged 21.45-113.20 mSv (median: 62.92 mSv) in Hodgkin lymphoma, 12.53-167.10 mSv (median: 52 mSv) in non-Hodgkin lymphoma, 4.13- 172.98 mSv (median: 52 mSv) in neuroblastoma, 31- 149.89 mSv (median: 63.10 mSv) in Wilms' tumor, 11.50- 73.72 mSv (median: 36.90 mSv) in germ cell tumor, 26.46- 125.86 mSv (median: 80.90 mSv) in other solid tumor and 0.02-13.31 mSv (5.25 mSv) in brain tumor subgroup. Twenty-two children (25%) died with progressive disease during the 5-year follow-up period.

Conclusions: Similar to previous studies, the total estimated effective doses in children with cancer have been found various according to diagnosis, stage and clinical course. To clarify the harmfull effects of radiation burden, prospective studies should be conducted in children with cancer.