Fetal Dose Estimation for Pregnant Breast Cancer Patients during Radiotherapy Using an In-house Phantom

Up to 3% of breast cancers may be diagnosed in pregnancy, during which period radiation therapy is not preferred, yet sometimes inevitable. Due to fetal radiation sensitivity, the fetal radiation safety is of particular concern. The present study was performed to estimate fetal dose for pregnant breast cancer patients during radiotherapy using an in-house phantom.

The fetal dose was estimated through phantom measurement using an ion chamber dosimeter. The phantom measurement was performed by simulating treatment planning on an in-house anthropomorphic phantom which consisted of natural human bone, cork, and paraffin. The right breast and the right supraclavicular area of the phantom were irradiated under the four-field technique with 6 and 10 MV photon beams for un-wedged and wedged fields.

During the first trimester of pregnancy, the radiation dose delivered to the fetus was in the range of 0.11-0.14 Gy for a 50 Gy total tumor dose in 25 fractions. The fetal dose in the second and third trimester of pregnancy ranged from 0.14-0.19 Gy to 0.22-0.32 Gy, respectively.

According to the results, the fetal dose is strongly dependent upon the energy beam, treatment procedure, and gestational stage