Hypofractionated Radiotherapy With Simultaneous-integrated Boost After Breast-conserving Surgery Compared to Standard Boost-applications Using Helical Tomotherapy With TomoEdge

Background/Aim: This comparative plan study examines a range of boost-radiation methods in adjuvant radiotherapy of breast cancer using helical intensity-modulated radiotherapy with TomoEdge-technique. Impact of hypofractionated radiation with simultaneous-integrated boost (SIB) and influence of differing assumed alpha/beta-values were examined. Patients and Methods: For 10 patients with left-sided breast cancer each four helical IMRT-plans with TomoEdge-technique were created: hypofractionated+SIB (H-SIB) (42.4154.4 Gy, 16 fractions), normofractionated+SIB (N-SIB) (50.4/64.4 Gy, 28 fractions), hypofractionated+sequential-boost (H-SB) (42.4 Gy/16 fractions+ 16 Gy/ 8 fractions), normofractionated+ sequential-boost (N-SB) (50.4 Gy/28 fractions+16 Gy/ 8 fractions). Equivalent doses (EQD(2)) to organs-at-risk (OAR) and irradiated mammary-gland were analysed for different assumed alpha/beta-values. Results: The mean EQD(2) to OAR was significantly lower using hypofractionated radiation-techniques. H-SIB and H-SB were not significantly different. H-SIB and N-SIB conformed significantly better to the breast planning-target volume (PTV) and boost-volume (BV) than H-SB and N-SB. Regarding BV, mean EQD(2) was significantly higher for all alpha/beta-values investigated when using H-SIB and N-SIB. Regarding PTV, there were no clinically relevant differences. Conclusion: Relating to dosimetry, H-SIB is effective compared to standard-boost-techniques.