Radiotherapy and pregnancy: 2025 update.

We present the updated recommendations of the Société française de radiothérapie oncologique (SFRO, the French society for radiation oncology) on radiotherapy and pregnancy. The occurrence of cancer during pregnancy is a rare event (approximately 1 in 1000 pregnancies). The risks for the embryo or the foetus depend on the gestational age at the time of irradiation. The main risks are malformations with microcephaly and mental retardation. There is also a risk of radiation-induced cancer in the unborn child. In the case of only supradiaphragmatic irradiation, radiotherapy can be performed most often in pregnant women without risk to the foetus. On the other hand, in the case of an indication for subdiaphragmatic irradiation, therapeutic termination of the pregnancy should be proposed. In all cases, when radiotherapy is chosen, a phantom estimation of the dose delivered to the foetus, confirmed by in vivo measurement, is recommended. Conformational radiotherapy is the preferred technique because of the lower dose delivered to the foetus (except for tumour locations where other techniques such as intensity-modulated radiotherapy are recommended).