Fetal Dose Estimation and Risk Assessment in Pregnant Patients Undergoing Radiotherapy: A Comprehensive Review

With increasing maternal age, the risk of cancer during pregnancy has risen, currently affecting approximately ۰.۱% of pregnancies. The most common cancers during pregnancy are breast cancer, cervical cancer, Hodgkin's lymphoma, leukemia, and melanoma. Radiotherapy is essential for treating breast cancer, cervical cancer, and Hodgkin's lymphoma, but fetal radiation exposure depends on the stage of pregnancy and dosage. Radiotherapy targeting tumors above the diaphragm can expose the fetus to secondary radiation, raising concerns about potential risks, including carcinogenesis. This review evaluates methods for estimating fetal radiation dose and the risks of radiotherapy during pregnancy. A comprehensive literature search without time restriction was conducted using databases such as Scopus, PubMed, and Web of Science, complemented by citation tracking in PubMed and Google Scholar. The review focuses on fetal dosimetry methods, including direct measurements using thermoluminescent dosimeters or large ionization chambers on physical phantoms and Monte Carlo simulations with computational phantoms to calculate fetal doses, emphasizing accurate replication of pregnant patient scatter geometry. Studies highlight the importance of the radiotherapy team's expertise in managing fetal dose, despite the rarity of cancer during pregnancy. Accurate dose estimation is key to minimizing fetal exposure while ensuring effective treatment for the mother. Keeping fetal exposure below ۰.۱ Gy, ideally under ۰.۰۵ Gy, reduces risks, and radiotherapy is safest after the ۲۵th week of gestation. Various dosimetry methods have proven effective in maintaining these safety thresholds. Optimizing radiotherapy in pregnant cancer patients requires balancing the potential effects on the fetus with the stage and prognosis of the mother’s disease, as well as the risks associated with modifying cancer treatment. A thorough understanding of radiation's complex impacts on the fetus, informed by animal studies, clinical exposures, and data from atomic bomb survivors, is essential. Accurate estimation of fetal dose and comprehensive risk assessment are critical for informed decision-making, ensuring that the fetus is adequately protected while achieving the best possible treatment outcomes for the mother.

کلیدواژه ها:

Fetal dose ، Radiotherapy ، Pregnancy