2881

Abstract

CSI with photons may result in ovarian dysfunction and infertility due to radiation beam divergence into the true pelvis. However, reports of dosimetric analyses of the radiation received by the ovaries in such cases are lacking. The use of adjuvant chemotherapy may further increase the risk of ovarian failure. Laparoscopic ovarian transposition removes the ovaries from direct radiation exposure and, therefore, provides an option to preserve ovarian function. In this study, we report the radiation dosimetry of the ovaries before and after transposition in a female patient with medulloblastoma who underwent CSI. A 31 year-old nulliparous woman underwent complete surgical resection for a standard risk medulloblastoma of the left medial cerebellum and was offered CSI followed by chemotherapy. Computed tomography (CT) simulation was used for treatment planning and dose-volume histograms were generated. Before transposition, MRI of the pelvis demonstrated that both ovaries were within the spinal radiation field. Via laparoscopic transposition, the left ovary was placed adjacent to the lower pole of the left kidney while the right ovary was placed at the lower edge of the liver. Surgical clips at the most cephalad and caudal aspect of the ovaries permitted their localization on CT-simulation. The prescribed dose to the craniospinal axis was 2340 cGy with a posterior fossa boost of 3060 cGy delivered at 180 cGy per fraction using 6 MV photons. The mean, median and maximum doses for both ovaries before and after transposition are shown in Table 1. Before transposition, the mean and maximum doses to the ovaries corresponded to 42% and 69.4% of the prescribed dose of 2340 cGy for the left and to 7.1% and 30.9% of the prescribed dose for the right ovary, respectively. Ovarian transposition decreased the mean and maximum doses to 2.9% and 3.6% of the prescribed dose for the left and to 3.7% and 4.4% of the prescribed dose for the right ovary, respectively.Table 1Mean Total Dose (cGy)Median Total Dose (cGy)Maximum Total Dose (cGy)Left Ovary98310531624Left Transposed Ovary687084Right Ovary166129723Right Transposed Ovary8787103 Open table in a new tab This is the first report of three-dimensional dosimetric analysis of radiation dose delivered to the ovaries from CSI before and after lateral ovarian transposition. Given the significant reduction in ovarian dose following transposition, we recommend obtaining an MRI of the pelvis for ovarian localization in females who require CSI with photons. Ovarian transposition should also be considered as an option to maintain hormonal ovarian function and fertility in those cases where ovarian irradiation is otherwise unavoidable.