SU-F-T-499: Anatomic Features for Selection of Electronic Tissue Compensation Radiotherapy in Early-Stage Breast Cancer Patients After Breast-Conserving Surgery.

PURPOSE: To explore the correlations between anatomic features and dose-volumetric parameters in 3DCRT and eComp whole breast irradiation and identify the feasibility of anatomic parameters to predict the planning method selection.

METHODS: We compared the effectiveness between conventional three-dimensional conformal radiotherapy (3DCRT) and electronic tissue compensation (eComp) for whole breast irradiation. 3DCRT and eComp planning techniques were used to generate treatment plans for 60 whole breast patients, respectively. The planning goal was to cover 95% of the planning target volume (PTV) with 95% of the prescription dose while minimizing dose to lung, heart, and skin. Statistical analyses were performed between critical organ doses and patient anatomic features, i.e., central lung distance (CLD), maximal heart distance (MHD), maximal heart length (MHL) and breast separation (BS).

RESULTS: Comparing to 3DCRT plans, on the average, eComp treatment planning process was about 7 minutes longer, but resulted in lower lung V20Gy, lower mean skin dose, with similar heart dose. The benefits were more pronounced for larger breast patients. To keep the lung V20Gy lower than 20% and mean skin dose lower than 85% of the prescription dose, eComp was the preferred method for patients with more than 2.3 cm CLD or larger than 22.5 cm BS.

CONCLUSION: The study results may be useful in providing a handy criterion in clinical practice allowing us to easily choose between different planning techniques to satisfy the planning goal with minimal increase in complexity and cost. This study was supported by National Natural Science Foundation of China (NO. 31420103915) and Chongqing Health and Family Planning Commission Project (2015MSXM012).