Monte Carlo Simulation of Radiotherapy for Breast Cancer in Pregnant Patients: How to Reduce the Radiation Dose and Risks to Fetus?
This study estimated the fetal dose and risks from radiotherapy for breast cancer with 6 MV X-rays. Breast irradiation was simulated with the MCNP code using two mathematical phantoms corresponding to patients in the early and middle periods of pregnancy. Monte Carlo simulations were performed to determine the appropriate fetal shielding. For a 50-Gy tumor dose, the unshielded fetal dose reached up to 133.1 mGy. Fetal protection with a lead shield of dimensions 30 × 30 × 5 cm3 placed besides the treatment couch resulted in maximum doses of 22.0 and 70.3 mGy at the first and second trimesters of gestation, respectively. These shielded fetal doses may be associated with a fatal cancer risk during childhood up to 0.42% and a maximum probability for the appearance of heritable effects of 0.17%. The use of fetal shielding ensures the absence of deterministic effects from radiotherapy during the first 24 weeks of gestation.
Department of Medical Physics, Faculty of Medicine, University of Crete, PO Box 2208, 71003Iraklion, Crete, Greece.
Michalis
M
Mazonakis
Department of Medical Physics, University Hospital of Iraklion, 71110Iraklion, Crete, Greece.
Antonis
A
Tzedakis
Department of Medical Physics, Faculty of Medicine, University of Crete, PO Box 2208, 71003Iraklion, Crete, Greece.
John
J
Damilakis
D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D005333:Fetus; D006801:Humans; D009010:Monte Carlo Method; D019047:Phantoms, Imaging; D011247:Pregnancy; D011252:Pregnancy Complications, Neoplastic / Q000532:radiotherapy*; D011829:Radiation Dosage; D012306:Risk