Boost Delineation in Breast Radiation Therapy: Isotropic Versus Anisotropic Margin Expansion

Purpose/Objective(s): Bilateral cancer breast irradiation is a real challenge in the field of radiation therapy, especially in case of axillary nodes involvement. VMAT is an interesting technique to achieve suitable target volume coverage while sparing organs at risk (OAR) when compared to 3D-conformal radiation therapy. Here, we present results of treatment planning of 20 consecutive bilateral breast cancer patients treated in our institution. Materials/Methods: Twenty consecutive bilateral breast cancer patients were treated using VMAT technique from July 2011 to December 2013. Target volumes (CTV, GTV) were delineated according to RTOG guidelines. The prescribed doses were 63.2 Gy to PTVof boost (n Z 17), 52.2 Gy to PTVof whole breast (n Z 20) and of internal mammary chain (IMC) nodes (n Z 9) and 49.3 Gy to PTV of the supraclavicular (SC) nodes (n Z 9) in 29 fractions. The V95% for CTV breast should be larger or equal to 99% and V95% for all other CTVs larger or equal to95%. Values of PTV and OAR exposure were collected. Results: Main results are summarized in the following table.