Three-dimensional conformal hypofractionated simultaneous integrated boost in breast conserving therapy: results on local control and survival.

PURPOSE To report on local control and survival after breast conserving therapy (BCT) including three-dimensional conformal simultaneous integrated boost irradiation (3D-CRT-SIB) and on the influence of age on outcome. PATIENT AND METHODS For this study, 752 consecutive female breast cancer patients (stages I-III), treated with 3D-CRT-SIB at the University Medical Center Groningen from 2005 to 2008, were retrospectively identified. Median age was 58.4 (range 26-84) years. The SIB fractionation used was: 28×1.8Gy (whole breast) and 28×2.3Gy or 2.4Gy (tumour bed). Next to outcome, we estimated the effect of age on the recurrence-free period (RFP) by multivariate Cox regression survival analysis. RESULTS Median follow-up was 41 (range 3-65) months. Local control was 99.6% at 3 years (6 ipsilateral recurrences). The 3-year locoregional control, RFP and overall survival (OS) rates were 99.2%, 95.5%, and 97.1%, respectively. In multivariate analysis, tumours >2cm (hazard ratio (HR) 3.11; 95% confidence interval (CI) 1.57-6.17) and triple negativity (HR 3.03; 95% CI 1.37-6.67) and not age were associated with impaired RFP. CONCLUSIONS At 3 years, the 3D-CRT-SIB technique in BCT results in excellent local control and OS. Age was not a risk factor for any recurrence.