ESTRO 2020 Abstract book

S547 ESTRO 2020

PO-0938 Deep Inspiration Breath Hold (DIBH) as a standard option in left breast cancer patient (LBCP) A. Huscher 1 , L. Donadoni 1 , A. Taddeo 2 , M. Galelli 3 , T. Prochilo 4 , F. Guerini 5 , S. Mutti 5 , A. Zaniboni 6 , M. Bignardi 1 1 Fondazione Poliambulanza, Radiation Oncology, Brescia, Italy ; 2 University of Brescia, Radiation Oncology Chair, Brescia, Italy ; 3 Fondazione Poliambulanza, Medica Physics, Brescia, Italy ; 4 Fondazione Poliambulanza, Medical Oncology, Brescia, Italy ; 5 Fondazione Poliambulanza, Surgery, Brescia, Italy ; 6 Fondazione Poliambulanza, Oncology Department, Brescia, Italy Purpose or Objective To evaluate feasibility, treatment compliance and organs at risk sparing in LBCP treated with DIBH (Elekta ABC ® ) in 459 LBCP treated with ABC ® from 2012 to September 2019 were included in a retrospective analysis. Clinical Target Volumes (CTVs) contouring for breast, chest wall and nodal areas followed ESTRO Guidelines. Whole breast or chest wall CTVs were irradiated, either with 3D conformal technique (3D) or intensity modulated techniques (IMRT). Irradiation of breast/chest wall with nodal areas was always performed with IMRT. Hypofractionation (42.4 Gy in 16 fractions) was prescribed in most cases of whole breast irradiation while 50 Gy in 25 fractions were prescribed in any case of nodal irradiation. Clinically positive internal mammary nodes (IMN) were treated with a Simultaneous Integrated Boost technique (SIB) with doses of 55/50 Gy in 25 fractions. A 9 Gy boost (in 3 fraction) to tumor bed was used when indicated. 3D Treatment planning was performed through Elekta Xio ® and Elekta Monaco ® , while IMRT plans with Elekta Monaco ® . On board imaging included portal imaging for 3D technique and CBCT for IMRT and VMAT. In all cases a standard protocol was applied. Dose metrics for heart and left lung were analyzed, as well as ABC parameters.. Results ABC ® from 2016 represents the standard approach to LBCP irradiation with up to 85% of LBCP treated in the latest years with this technique; in 10% of cases we use prone irradiation or thermoplastic breast mask but about 5% of patients do not show adequate compliance for DIBH. Mean patient age was 56 years (range 28-85 years). Target volumes included in 304 the whole breast, in 28 the chest wall, in 77 the chest wall and supraclavicular nodes, in 43 breast and supraclavicular/axillary nodes and in 7 cases IMN. Hypofractionation was delivered in 252 cases, SIB in 2 cases and the remaining received conventional fractionation. 3D accounted for 53% of treatments while IMRT for 47%. Planned Target Volume mean value was 818 cc (range 2352-162), ABC ® threshold had a mean and median of 1423 and 1500 (range 1000-2000 cc); breath hold time showed mean and median values of 24 and 25 seconds (range 18- 30 s). Lung reference constraints, depending on clinical prescriptions and fractionation, were always respected, and mean left lung dose was 8.2 Gy, (range 4-13.9 Gy). Heart reference constraints, depending on fractionation (V 20Gy for hypofractionation and V 25 Gy for standard fractionation), were always lower than 5% and mean heart dose was 3 Gy, (range 0.9-7, this latter in case of IMN irradiation). All radiation sessions were completed in a 15 minutes slot. Conclusion Routine use of DIBH with ABC ® is feasibile in real time practice and effective in achieving respect of organs at risk. daily clinical practice. Material and Methods

PO-0939 Structured prospective database:exploratory study about toxicity and progression in breast patients. M. Lizondo 1 , J. Fuentes-Raspall 2 , A. Soto 2 , N. Jornet 3 , A. Latorre-Musoll 3 , P. Delgado-Tapia 3 , P. Carrasco 3 , J. Pérez-Alija 3 , P. Gallego 3 , P. Simón 3 , A. Ruiz-Martínez 3 , M. Adrià 3 , I. Valverde-Pascual 3 , M. Barceló 3 , N. Garcia 3 , M. Ribas 3 1 Institut de Recerca Hospital de la Santa Creu i Sant Pau, Servei de Radiofísica i Radioprotecció, Barcelona, Spain ; 2 Hospital de la Santa Creu i Sant Pau, Servei d'Oncologia Radioteràpica, Barcelona, Spain ; 3 Hospital de la Santa Creu i Sant Pau, Servei de Radiofísica i Radioprotecció, Barcelona, Spain Purpose or Objective Predictive toxicity models in radiation therapy have to be built and validated using clinical and dosimetry data. But the data reported in medical records lacks, most of the time, of structure and therefore it is difficult to use. In our institution, five years ago, we implemented a systematic way to prospectively collect structured data related to the RT patient treatment (cofounding clinical factors, oncological information, treatments, RT specific data and follow-up information) using RedCap. The analysis of this database let us to evaluate clinical outcome of breast cancer patients after treatment and which factors are related with acute/late toxicity and progression disease. Material and Methods From May 2013, 622 breast cancer patients treated in our institution with radiotherapy (Clinac2100CD,Varian) were prospectively included in the database. For this study the mean follow-up was of 3 years. A group description is shown in Table1. Baseline patient characteristics were recorded as well as clinical breast cancer information and local outcome after surgery but prior to start RT. Dosimetry data was also automatically transferred from Eclipse TPS to the database. Acute toxicity was recorded during treatment and late toxicity on a yearly follow-up. Acute/late toxicities were evaluated following the Common Terminology Criteria for Adverse Events (CTCAE v.3.0): skin toxicity (dermatitis, hyperpigmentation) and late-fibrosis. Risk factors for skin toxicity and fibrosis were investigated, considering the maximum toxicity grade presented during the treatment for skin toxicity, and during the first 2.5- year-follow-up for fibrosis. Progression disease included local recurrence and metastasis. Risk factors for progression disease were also studied. Associations were assessed with Chi-square or Fisher’s exact test for categorical factors, and with Krustall-Wallis test for quantitative factors.