Adaptive Lumpectomy Boost Planning Can Reduce Normal Tissue Exposure in Patients Receiving Hypofractionated Whole Breast Irradiation.

BACKGROUND/AIM: To evaluate the change in lumpectomy cavity (LPC) volume during hypofractionated radiation (Hypo-RT) and assess the dosimetric benefits of adaptive boost planning on normal tissue exposure in breast cancer patients. PATIENTS AND METHODS: Two separate computed tomography (CT) simulation scans were obtained. The first (CT1) was used to plan whole breast irradiation, and the second (CT2) was used to plan LPC boost. LPC boost treatment planning was performed on both CT1 and CT2. RESULTS: Mean LPC volume was significantly smaller on CT2 compared to CT1. LPC boost plan comparison showed significant reductions from CT1 to CT2 in mean heart dose and mean lung dose. Mean volume of tissue receiving 95% of the prescribed boost dose (V95) was lower on CT2 (p=0.001), as was V80 (p<0.001) and V50 (p<0.001). CONCLUSION: LPC volume can change significantly during Hypo-RT. Adaptive LPC boost planning can be considered to reduce normal tissue exposure.