ESTRO 38 Abstract book

S394 ESTRO 38

proportional hazards regression model of ipsilateral locoregional recurrences. Only significant characteristics are presented. Abbreviations: PR = progesterone receptor; ER = estrogen receptor. Conclusion A 9 Gy IOERT boost combined with post-operative WBI provided outstanding local control rates, comparable to all trials with similar length of follow up. Furthermore, this is the largest cohort reporting on late toxicity and cosmetic outcome; our results demonstrate IOERT boost to be well-tolerated, with limited late toxicity and an excellent cosmetic outcome. PO-0766 The Italian Society of Radiation and Clinical Oncology (AIRO): snapshot on breast cancer management F. Gregucci 1 , A. Fozza 2 , S. Falivene 3 , D. Smaniotto 4 , A. Morra 5 , A. Daidone 6 , R. Barbara 7 , A. Ciabattoni 8,9 1 Sacro Cuore Don Calabria - IRCCS, Radiation Oncology, Negrar, Italy ; 2 ASO S.S. Antonio e Biagio e Cesare Arrigo, Radiation Oncology, Alessandria, Italy ; 3 P.O. Ascalesi, Radiation Oncology, Napoli, Italy ; 4 Policlinico Universitario A. Gemelli IRCCS - Università Cattolica del Sacro Cuore- Istituto di Radiologia, Radiation Oncology, Roma, Italy ; 5 Istituto Europeo di Oncologia – IRCCS, Radiation Oncology, Milano, Italy ; 6 P.O. Abele Ajello, Radiation Oncology, Mazzara del Vallo, Italy ; 7 AO San Giovanni Addolorata, Radiation Oncology, Roma, Italy ; 8 Ospedale San Filippo Neri, Radiation Oncology, Roma, Italy ; 9 on the behalf of Italian Society of Radiation and Clinical Oncology AIRO Breast Group, Radiation Oncology, Italy, Italy Purpose or Objective To investigate the actual attitude of the Italian Radiation Oncologists in the management of breast cancer (BC) concerning some controversial issues. Material and Methods A nationwide, 21-points questionnaire was distributed online via Survey Monkey to the Italian Radiation Oncologists. Results 78 Centers answered the Survey for 34164 patients (pts) affected by BC. In most centers, the pts number treated was superior to 200/year and in almost all cases an experts multidisciplinary discussion was performed to choose the best treatment for each patient. 16734 (49%) pts were treated with hRT. The 95% of centers used this treatment approach as clinical practice after breast-conserving surgery (BCs) for early stage BC, mostly in women older than 50 years (40%) affected by invasive ductal carcinoma (IDC) (89%). Dose prescription ranged between 34-45Gy with high use of moderate hRT (40Gy/15fr and 42.4Gy/16fr in 62% of cases). In locally advanced BC, the post-mastectomy or regional nodal hRT was still rarely applied, 13% and 15% respectively. In early stage BC, the 60% of centers used partial breast RT (PBI) with different techniques. 216 (0.6%) pts received rRT after BC recurrence. In 80% of cases, the rRT was given more than 5 years after primary RT. The age factor was not related with the rRT choose (68% of answer were “all age”) and the most frequent histological type was IDC (82%) alone or associated with other histology. Regarding RT volumes are so representative below: 54% total rRT (WBI/chest wall irradiation) and 94% PBI (including 42% of tumor bed RT). 3879 (11%) pts received RT after NAC. In the 55% of cases a clinical disease evaluation was performed at the end of NAC and in 40% before. Disease staging included sentinel node biopsy before and after NAC in 40% and 60% respectively. The chest wall and the ipsilateral lymph nodes RT is a shared choice by most of the Italian Radiation Oncologists in case of locally advanced BC at the disease onset (cT3-T4 and/or cN2-N3), regardless of the kind of response obtained after NAC (complete response vs partial response) and also independently by the axillary

Belgium ; 2 GZA Hospitals, Gynaecology, Antwerp, Belgium ; 3 Antwerp University Hospital, Multidisciplinary Oncologic Centre Antwerp MOCA, Edegem, Belgium ; 4 GZA Hospitals, Oncology, Antwerp, Belgium ; 5 University of Antwerp, Center for Oncological Research, Antwerp, Belgium ; 6 Oncology Center GZA, Translation Cancer Research Unit, Antwerp, Belgium Purpose or Objective Advantages of using intraoperative radiotherapy with electrons (IOERT) as a boosting modality in breast- conserving therapy, include the direct visualization of the tumor bed, patient convenience, and allows a reduced dose to the skin, which may lead to a more favorable cosmetic outcome. We aimed to report oncological outcome, postoperative complication rate, mammographic changes on follow-up imaging, late toxicity and cosmetic outcome in women treated at our institution with IOERT as a boost modality in breast- conserving therapy for early invasive breast carcinoma or ductal carcinoma in situ (DCIS). Material and Methods Between January 2007 and June 2018, 763 unselected patients of any risk group with early breast carcinoma or DCIS, treated at the GZA Hospitals were enrolled. During breast-conserving surgery, an IOERT boost of 9 Gy (90% reference dose) was applied, followed by whole breast irradiation (WBI). In a subset of patients (n=230) late toxicity and cosmetic outcome were scored prospectively using the LENT-SOMA breast questionnaires. Results At a median follow-up of 62.2 months (range: 0.5 – 135), only 12 in-breast recurrences were observed, yielding a local tumor control rate of 98.4% at 5 years. A DFS of 95.1% at 5 years and OS of 97.2% at 5 years were noted. In univariate analysis, negative ER status, adjuvant hormonal therapy and interval between IOERT and EBRT predicted ipsilateral locoregional recurrence (Figure 1), albeit in multivariable analysis none reached significance. From the 12 patients with an in-breast recurrence, 9 were located within the initially involved quadrant and 3 outside this quadrant. A total of 27 (3.5%) patients developed postoperative complications (e.g. hematoma, infection, wound dehiscence). None of the tumor characteristics nor any of the IOERT technical parameters were predictive for postoperative complications. Ninety-nine percent of patients received follow-up imaging with a frequency < 2/year (median 0.92/y, range: 0 – 5.5). On follow-up imaging, 179 patients with mammographic changes were found of which 57% (n=102) required a biopsy. After a median follow-up of 35 months (range: 22-64), the most prevalent G2 toxicities were breast fibrosis (29.5%) and breast pain (6.9%). Only 5.4% of patients reported any kind of G3 toxicity. A total of 78.8% patients had an excellent to good cosmetic outcome.

Figure 1. Forest – Plot: Hazard ratios (HR) and 95% confidence intervals (CI) obtained from univariable Cox