J.L. Lopez Guerra

EP-1049: Application of artificial intelligence for breast cancer classification before adjuvant radiation therapy

Purpose/Objective: Different techniques of accelerated partial breast irradiation have been described in the literature. Using a volumetric modulated arctherapy technique (VMAT) allow a better target coverage and better protection of critical organs compare to threedimensional conformal radiotherapy (RC3D). We present here the dosimetric results of the first patients treated with CRLC Val dAurelle in Montpellier for an accelerated treatment (IPAS). Materials and Methods: Between may 2011 and July 2012, ten patients were treated by IPAS for breast cancer using a VMAT technique. Dose was 40 Gy, 4 Gy per fraction twice fractions per day separate from 6 hours, spread over a week. PTV was generated by expansion of the lumpectomy cavity of 1.8 cm. Treatment was delivered by two arcs of 270 degrees using the technology RapidArc (Varian 21 EX) with a collimator rotation of 45 degrees. The optimization and dose calculation were performed with version 10.0.28 of the planning system and Eclipse AAA algorithm with a 2.5 mm calculation grid. The constraints were for the PTV D99% ≥ 95%, D95% ≥ 100% of the prescribed dose. For the ipsilateral lung: V20Gy <3% V10Gy <10% V5Gy <20% and V20Gy <1% V10Gy <2% V10Gy <3% for the contralateral one. Concerning the eart for V20Gy <1% V5Gy <70%. Results: The average volume of the PTV was 99.9 cc [39.8 to 219.5] (mean and range). An average of 95% of the PTV received 99.7% of the prescribed dose [99.4 to 99.9]. Hotspots: V110Gy represented 0.34% [0 to 1.42] PTV. The homogeneity index defined as: HI = (D2% D98%) / D median was 0.056 [0.040 to 0.085]. The dose to healthy tissues (OAR) was optimal. For the ipsilateral lung V20Gy was 0.27% [0 to 2.67], the V10Gy 1.60% [0 to 10.47], 6.17% V5Gy [0 to 19.94] . Regarding the contralateral lung V20Gy and V10Gy are equal to 0% and V5Gy to 0.28% [0 to 2.78]. For the heart V5Gy was 3.10% [0 to 23.59], all other constraints were largely reached. The average number of monitor unit was issued 580UM [473-655] and the processing time was 3.2 minutes for two arcs. Conclusions: IPAS by RapidArc provides excellent coverage of the PTV while preserving healthy tissue. Processing speed improves its quality because intrafractions movements are reduced. We have not observed severe acute toxicities.