Ovary-Sparing Radiation Planning Techniques Can Achieve Ovarian Dose Reduction for Soft Tissue Sarcoma of the Buttock and Thigh

Background and Objectives. Attention to ovary dose is important for premenopausal women undergoing radiation therapy (RT) and must not be overlooked when treating extremity sarcoma. We assessed whether ovary-sparing RT plans could decrease ovary dose without compromising target coverage. Methods. Standard sarcoma target volumes and organs at risk (OAR) were contoured by a sarcoma dedicated radiation oncologist on CT planning scans for 23 women with thigh or buttock sarcoma. IMRT plans (50 Gy) with and without attempted ovary-sparing were created by an expert sarcoma dosimetrist. Results. All plans met target coverage goals. Compared to standard plans, ovary-sparing plans had lower mean bilateral ovary doses (MBOD) (652 versus 483 cGy, p=0.007) but higher bone doses (mean V50: 8.5% versus 6.9%, p=0.049) and lower conformity indexes (1.12 versus 1.19, p=0.009). Tumors < 8 cm from the pubic symphysis had significant MBOD reduction with ovary-sparing plans (376 cGy versus 619 cGy, p=0.0184). On multivariate analysis, distance to pubic symphysis and proximal medial thigh site were associated with MBOD reduction with ovary-sparing plan. Conclusions. For preoperative IMRT, ovary-sparing planning significantly reduces ovarian dose in women with sarcoma of the proximal thigh and near the pubic symphysis.