ESTRO 2020 Abstract book

S567 ESTRO 2020

Results Median GLS was -20.5% [-16 ; -28.5] before RT and -20.2% [-8.2 ; -29.4] 6 months after with a mean variation of -1.1% [-18.3 ; +6.1.]. As defined, 6 patients (7.8%) had GSL alteration at 6 months. AB, SB, AM and A segments showed significantly more alterations than the other segments. Regional alterations are summarized in table 1. Mean Dmean in altered segments was significantly higher the non-altered segments 7.7Gy vs 5.4Gy (p=0.02). Conclusion The results of our study show that radiation dose to the different heat segments is correlated with their subclinical alteration. Global heart delineation seems to be insufficient during the planning of breast radiotherapy. Segmental delineation of the LV may be an interesting alternative to limit segmental doses to reduce the risk of subclinical alterations. A mean dose of 5 Gy could be proposed in exposed heart segment. PO-0979 Variability of axillary nodal CTV contouring in breast cancer (PART I - geometric evaluation) M.C. Leonardi 1 , F. Cattani 2 , M. Pepa 1 , R. Luraschi 2 , S. Vigorito 2 , S.G. Gugliandolo 1 , D. Ciardo 1 , R. Orecchia 3 , B.A. Jereczek-Fossa 1 , A. Breast Cancer Study Group 4 1 IEO- European Institute of Oncology IRCCS, Division of Radiotherapy, Milan, Italy ; 2 IEO- European Institute of Oncology IRCCS, Department of Medical Physics, Milan, Italy ; 3 IEO- European Institute of Oncology IRCCS, Scientific Directorate, Milan, Italy ; 4 Associazione Italiana di Radioterapia e Oncologia Clinica, Airo, Milan, Italy Purpose or Objective To determine the interobserver variation in axillary lymph node definition in breast cancer (BC) by comparing the nodal single centre CTV (SCCTV, drawn by radiation oncologists, ROs, of each participating institution) with the nodal gold-standard CTV (GSCTV). Material and Methods This analysis was an expansion from a previous study, where the axillary nodal variability between institutions and observers was investigated for three representative patients, P1, P2, P3, with increasing level of anatomic complexity, and it formed the basis for further dosimetric assessment. In the present analysis, a GSCTV, created in DICOM format by the median of all the axillary nodes CTVs drawn by the BC experts of the radiotherapy (RT) centres originally involved, was reviewed by 3 independent BC experts and one radiologist to reach a consensus and validated using the STAPLE outline. For each case patient, the nodal CTVs (SCCTV) drawn by 18 ROs, all of them already participating in the previous work, were chosen to make comparison with GSCTV. For each patient and each centre, contours of the three considered node levels (L2, L3 and L4) and the CTV, both as SC and GS, were retrieved from MIM software version 6.1.7 (MIM Software, Cleveland, OH) and subsequently imported into ImSimQA software (v4.2, Oncology Systems Limited, Shrewsbury, UK), to compute the following metrics: conformity index (CI), mean distance to conformity (MDC), volume difference (Vol.diff(%)), DICE similarity coefficient (DICE), sensitivity index (Se.Idx) and inclusion index (Incl.Idx). Results A total of 18 RT centres partecipated in the study. For each centre, SCCTV and the GSCTV of each corresponding representative patient were compared (Table 1). Overall, in P1 and P2 the CTV volume was significantly underestimated by the ROs (-29.25% and -27.83%, respectively), whereas in P3 it was only slightly overestimated (+12.53%). Nevertheless, the degree of superposition of contours, and therefore the quality of Segment AB AM SB SM PB PM A Alteration 29 19 23 8 7 4 18

HER2-negative, tumor histological grade G1-G2, R0 resection, staged pT1-T2 pN0 cM0, with an adequate dosimetric study. A dose of 40Gy was delivered in 15F (2.67Gy/F) followed by a boost to the tumor bed of 10- 16Gy in 5-8F (2.0Gy/F). Acute toxicity (CTCAE5.0 scale) and heart and lung dosimetric parameters were recorded. Survival analysis by the Kaplan-Meier method. Results Of the 215 patients accepted for HRT, 9 were excluded. 206 included patients with a median age 64 years (50-83 years); left side tumors in 51.9%; upper quadrants in 40.8%. Invasive carcinoma not otherwise specified (NOS) present in 84.5%; stage pT1b in 33.0% and pT1c in 51.5%. A 10Gy boost was prescribed in 53.4% of patients. The median values of the dosimetric parameters evaluated were heart V25 of 3.56% (0%-19.7%) and ipsilateral lung V20 of 11.68% (1.7%-24.38%). All patients completed the initially planned schedule, 97.6% presenting acute cutaneous toxicity (any grade), grade 3 in 7.8%. No other side effects were registered during treatment. Median follow-up was 21 months (2-60 months). In the first follow- up appointment toxicity was registered in 55.8% patients, with erythema/pigmentation grade 1-2 in 17.0% and grade 3 in 1.0%, breast edema in 30.1% and scar fibrosis in 8.7%. One patient had symptomatic radiation pneumonitis, with full resolution after therapy. In subsequent follow-up appointments, there was hyperpigmentation in 7.8%, breast edema in 24.3%, scar fibrosis in 14.1% and telangiectasia in 2.9%. At two years follow-up: LRDFS 100%, DFS 99.4%, OS 98.6% and DSS 99.3%. Conclusion Hypofractionated radiation therapy allows for excellent treatment compliance with an acceptable toxicity profile. Oncologic outcomes and late toxicity results are similar to those described for conventional fractionation, making HRT a strong option in this subset of breast cancer patients in real-life settings. PO-0978 Is there a correlation between radiation doses and heart segmental alterations at 6 months? N. Fourati 1 , I. Chafaii 1 , S. Charfeddine 2 , L. Abid 2 , S. Kammoun 2 , W. Mnejja 1 , D. Jamel 1 1 Faculté de médecine Université de Sfax, Radiotherapy Oncology Department- Habib Bourguiba Hospital, Sfax, Tunisia ; 2 Faculté de médecine Université de Sfax, Cardiology Department- Hedi Chaker Hospital, Sfax, Tunisia Purpose or Objective The aim of our study was to evaluate sub-clinical cardiac alterations detected by speckle tracking echocardiography (STE) and to determine if there is a correlation between the doses received by the different segments of the left ventricle (LV) and the alterations at their level after breast cancer radiotherapy (RT). Material and Methods A total of 77 female patients with non-metastatic breast cancer were prospectively followed and evaluated. All patients received 3D conformal RT to deliver 50 Gy in 25 fractions ± 16 Gy boost. Forty seven patients (61%) had left sided RT and 71 patients (92%) received chemotherapy prior to RT. Whole LV was initially delineated and then divided into 7 different segments: the antero-basal (AB), antero-median (AM), septo-basal (SB), septo-median(SM), postero- basal(PB), postero-median (PM), and apical (A) segments. The mean dose (Dmean) of different segments was reported. All patients had STE before RT and 6 months after. A LV global longitudinal strain (GLS) alteration was defined as a reduction of more than 10% from the initial value. We then proceeded to a qualitative evaluation of the Bull’s eye alteration of different segments. Independed-sample T test was used to compare mean Dmean doses according to the alteration of the different segments.