Fetal dose assessment in radiotherapy: A systematic review and results of survey on assessment tools and methods, dose ranges, optimization strategies and imaging dose

PURPOSE: This study aimed to identify the methods currently used to evaluate fetal dose in pregnant patients undergoing radiotherapy, the strategies implemented to optimize fetal exposure, and the fetal dose ranges reported in the literature. MATERIALS AND METHODS: A systematic review was conducted and complemented by a survey. Data related to fetal-dose assessment, optimization approaches, and reported fetal-dose levels were extracted and analyzed. RESULTS: Seventy-eight studies were included in the systematic review, and twelve clinical cases were collected through the survey. In the literature, fetal-dose evaluation most frequently relied on measurements performed in anthropomorphic phantoms using passive dosimeters and ionization chambers. Among published clinical case reports, in-vivo dosimetry was commonly implemented to monitor fetal exposure. Several strategies were found to substantially reduce fetal dose, including the use of shielding blocks, flattening-filter-free beam modes instead of flattened beams, and collimator-angle optimization. Overall, most estimated fetal doses were well below 100 mGy, regardless of tumor site or treatment technique. The lowest fetal doses were reported with proton pencil beam scanning, while optimized IMRT and VMAT plans achieved fetal exposures comparable to those obtained with 3DCRT. CONCLUSION: This systematic review and survey provide a comprehensive overview of current fetal-dose assessment methods and optimization strategies in radiotherapy. The lack of up-to-date recommendations adapted to modern radiotherapy highlight the need for practical guidance. As part of the SONORA project, the development of a dedicated leaflet will support medical physicists by providing structured, practical recommendations to ensure safer and more consistent management of radiotherapy during pregnancy.