Purpose/Objective(s): To explore the difference on acute radiation injury of the skin and cosmetic outcome after breast conserving therapy for early breast cancer between the simultaneous integrated boost intensity modulated radiation therapy (SIB-IMRT) and late-course boost intensity modulated radiation therapy (late-course boost-IMRT). Materials/Methods: For this study, 353 female breast cancer patients (stages I-II), treated with breast-conserving surgery at the institute between November 2002 and February 2012, were retrospectively identified. Median age at diagnosis was 43 (range 20-67) years. Two hundred eighteen patients were treated with SIB-IMRT after breast conserving therapy and 135 patients were treated with late-course boost-IMRT. The tumor bed was delineated and expanded with a margin of 10-15 mm to generate boost planning target volume (PTVt). The whole breast was expanded with a margin of 5 mm to generate the breast PTVb. For the SIB-IMRT group, fractionation schemes used were 27-28 daily fractions of 1.8-1.9 Gray (Gy) to the PTVb and 2.15-2.3 Gy to the boost PTVt. For the late-course boostIMRT group, fractionation schemes used were 25 daily fractions of 2.0 Gy to the whole breast PTVb, then 5-8 daily fractions of 2.0 Gy to the boost PTVt only. We estimated difference of the two groups on acute radiation injury of the skin and cosmetic outcome according to RTOG and Harris’ cosmetic criterion based on the Log-Rank and c test. Results: Median follow-up was 62 (range 1-144) months. The two groups had comparability on age, stages, histopathology, hormone receptor status, postoperative chemotherapy (all P value > 0.05). For all patients, OS was 98.71%, 96.68%, 94.51% at 3, 5, 10-years, respectively. DFS was 95.34%, 90.55%, 88.15% and LCR was 96.86%, 95.43%, 94.60% at 3, 5, 10-years for the whole group, respectively. The 3, 5, 10-year LRR were 3.13%, 4.57%, 5.4% and the DMR was 0.60%, 2.54%, 2.94% for the patients, respectively. There was no significant differences between the SIB-IMRT and late-course boost-IMRT group (X2 Z 0.01, P Z 0.91). For the acute radiation injury of the skin, there were 155, 56, 7 cases and 86, 43, 5 cases at 1, 2, 3 degree for the SIB-IMRT and late-course boost-IMRT group, respectively. There was no significant differences between the SIB-IMRT and late-course boost-IMRT group (X2 Z 1.85, P Z 0.40). Meanwhile, in cosmetic outcome, there were 187, 22, 8, 1 cases and 109, 17, 7, 1 cases at great, good, general, bad for the SIB-IMRT and late-course boost-IMRT groups, respectively. There was no significant differences between the SIBIMRT and late-course boost-IMRT group (X2 Z 1.29, P Z 0.30). Conclusions: In conclusion, SIB-IMRT had the same survival comparing with late-course boost-IMRT. Meanwhile, the acute radiation injury of the skin and cosmetic outcome was the same as late-course boost-IMRT. Therefore, it was worth to popularize in clinical. Author Disclosure: S. Wang: None. H. Xing: None. J. Li: None. Z. Ying Jie: None. M. Xu: None. Y. Ding: None. W. Wang: None.
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