ESTRO 2020 Abstract book

S541 ESTRO 2020

Nutritional Epidemiology Unit, Florence, Italy ; 3 Azienda Ospedaliero-Universitaria Careggi, Medical Oncology Unit, Florence, Italy ; 4 Azienda Ospedaliero-Universitaria Careggi, Breast Surgery Unit, Florence, Italy ; 5 Azienda Ospedaliero-Universitaria Careggi, Diagnostic Senology Unit, Florence, Italy ; 6 University of Florence, Pathology Unit, Florence, Italy Purpose or Objective Cyclin-dependent kinase 4/6 inhibitors (CDK4/6i), in combination with endocrine therapy (ET), currently represent the standard of care for I-II line metastatic hormonal receptor (HR)-positive HER2-negative breast cancer, demonstrating a significant improvement in terms of both progression-free (PFS) and overall survival (OS) when compared to ET alone. In the metastatic setting, radiation therapy (RT) is often required with either palliative or ablative intent, most in case of oligometastatic patients. The aim of our study was to evaluate the safety and efficacy of concomitant RT and CDK4/6i in metastatic HR+/HER2- breast cancer patients. Material and Methods We analysed 23 patients (for a total of 25 radiation treatments) consecutively treated in Our Institution with I-II line CDK4/6i and RT between September 2017 and August 2019. Both hematologic and non-hematologic toxicity have been evaluated (according to CTCAE v.5.0), along with PFS and OS. Results Median age of the series was 59 years (range 37-80). At the time of metastatic disease diagnosis, 19 patients (83%) were postmenopausal. Sixteen patients were treated with palbociclib, 7 with ribociclib. Fifty-two percent of patients received letrozole (I line) and 48% received fulvestrant (II line) as ET. Bone was the most frequently treated RT site (76%), followed by central nervous system (12%) and liver (8%), with 3-dimensional conformal radiation therapy (3D- CRT) as the most commonly technique used (56%). In 9 cases (36%) RT was given concomitantly to CDK4/6i, while in 16 cases (64%) CDK4/6i were suspended before or during RT. At a median follow up of 10.7 months (range 1.2-23.1), OS was 95.7% and PFS 69.6%. RT localization, techniques, palliative or ablative intent, and combination between RT and CDK4/6i were not significantly associated with OS and PFS. The combination of both ablative and palliative RT and CDK4/6i was not significantly associated with CDK4/6i dose reduction and with any toxicity graded >G2. Hematologic adverse events were the most commonly reported. In detail, 44% of patients developed neutropenia, most commonly >G2 (35%). Thrombocytopenia was reported for the 17% of patients and anemia for 26% (G1). Non-hematologic toxicity was less frequent: two patients experienced G2 diarrhea, and the most common non-hematologic event was G1 asthenia (22%). Conclusion Our study showed the safety and the efficacy of RT with either palliative or ablative intent combined with CDK4/6i plus ET, with a limited number of adverse events >G2 and data on PFS/OS comparable to those currently available in literature. Further studies on larger series are strongly needed to confirm these encouraging findings. PO-0929 Mammary chain irradiation: can we reduce the risk of secondary cancer and ischaemic heart disease? S. Corradini 1 , V. Figlia 2 , C. Simonetto 3 , M. Eidemüller 3 , S. Naccarato 2 , G. Sicignano 2 , A. De Simone 2 , R. Ruggieri 2 , R. Mazzola 2 , C. Matuschek 4 , E. Bölke 4 , M. Pazos 1 , M. Niyazi 1 , C. Belka 1 , F. Alongi 1 1 LMU Munich, Department of Radiation Oncology, Munich, Germany ; 2 IRCCS Sacro Cuore Don Calabria Hospital, Department of Advanced Radiation Oncology, Negrar-Verona, Italy ; 3 Helmholtz Center Munich, Institute of Radiation Medicine, Munich, Germany ;

Material and Methods Materials & Methods

A literature review was conducted for studies published from 2000-2019 to identify QIs relevant to breast cancer RT. Clinical data were automatically extracted and manually curated to record variables enabling assessment of selected QIs. The study population included all patients with invasive breast cancer who attended radiation oncology clinics at 4 NSW oncology centres (A,B,C,D) between 1/1/2018-30/6/2018. Descriptive and exploratory analyses were performed to measure breast cancer RT QIs and factors influencing QI compliance. 32 published QIs were identified with 22 selected for measurement, excluding 3 duplicate QIs, 1 not relevant to study population and 6 considered too difficult to measure. 20 selected QIs had published benchmarks. 15- 16 QIs were automatically extractable per institution with the remainder requiring manual extraction. 387 patients met the study criteria. Median age was 62 years, 79% had breast conservation and 86% were Stage I&II. Overall, benchmarks were met for 2 (10%) QIs (proportion of patients <50 years receiving RT boost after breast conservation surgery and proportion of left sided cancers with a recorded heart DVH) and were within 5% of benchmarks for an additional 4 (20%) QIs (proportion receiving RT after breast conservation surgery, proportion of pN0 patients receiving breast RT after breast conservation surgery, recording of decision regarding systemic therapy and proportion of patients with a focally positive margin receiving a boost). Compliance to QIs were <90% of target benchmarks for the remainder. Individual institutions met benchmarks for 4-6 QIs and were within 5% for an additional 1-5 QIs and within 10% for an additional 1-3 QIs. (Figure 1) On multivariate analysis, institution was the commonest factor associated with QI compliance being significant for 7 (35%) QIs. Results Results

Conclusion Conclusions

It was feasible to measure most QIs using automatic extraction of routinely collected data. Although the majority of QIs did not meet published benchmarks for the overall population, compliance was higher when analysed at the institutional level. There was institutional variation in QI compliant care. PO-0928 Safety and efficacy of concomitant RT and CDK4/6 inhibitors in metastatic breast cancer patients. L. Visani 1 , C. Saieva 2 , I. Desideri 1 , V. Scotti 1 , L. Dominici 1 , E. Scoccimarro 1 , M. Aquilano 1 , C. Cerbai 1 , V.E. Palmieri 3 , V. Maragna 1 , C. Becherini 1 , M. Bernini 4 , L. Sanchez 4 , L. Orzalesi 4 , J. Nori 5 , L. Antonuzzo 3 , S. Bianchi 6 , I. Meattini 1 , L. Livi 1 1 University of Florence, Department of Experimental and Clinical Biomedical Sciences, Florence, Italy ; 2 Cancer Research and Prevention Institute, Molecular and