ESTRO 2023 - Abstract Book

S1015

Digital Posters

ESTRO 2023

Conclusion 5-fraction schedule after BCS is well tolerated and the intensive 1-year cardiological monitoring showed no significant differences overtime in cardiac functioning.

PO-1270 Safety of Combination of Abemaciclib and Radiotherapy in metastatic breast cancer patients

S. Silipigni 1 , E. Ippolito 1 , J. Infante 1 , S. Carrafiello 1 , F. Pantano 2 , E. Onorati 1 , M. Fiore 1 , L. Cerasani 1 , V. Palumbo 1 , G. Tonini 2 , S. Ramella 1 1 Campus Bio-Medico Unicersity Hospital Foundation, Radiation Oncology, Rome, Italy; 2 Campus Bio-Medico Unicersity Hospital Foundation, Oncology, Rome, Italy Purpose or Objective Little evidence regarding safety and efficacy of the combination of CDKIs plus radiotherapy (RT) is still currently available. Moreover the majority of studies report on the association of RT with Palbociclib or Ribociclib, less on Abemaciclib. The aim of this study is to evaluate the early toxicity of concurrent use of radiotherapy in association with Abemaciclib in patients with hormone-receptors positive metastatic breast cancer. Materials and Methods Records of patients with histologically proven metastatic or locally advanced breast cancer treated in our institution were reviewed. Patients who received radiotherapy and concurrent Abemaciclib were selected. Toxicity was assessed according to the National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0 (NCI-CTCAE V4.0). Results Eighteen consecutive metastatic breast cancer patients treated to 31 metastatic sites were studied. All patients (n=16, 100%) received Abemaciclib during radiotherapy course. 68% of patients received full dose of Abemaciclib during radiotherapy. The majority of treatments (77.5%) had a palliative intent (median dose= 30 Gy, range= 8-30 Gy). Four patients (22.2%) were treated to oligo-metastatic or oligo-progressive sites of disease with higher biological effective dose by stereotactic body radiotherapy (SBRT) (median dose = 30 Gy, range 21-30 Gy given in 3-5 fractions). Two patients (12.5%) were treated to chest wall skin disease (total dose 45 Gy). Two patients suspended RT and Abemaciclib due to haematological toxicity (one G3 neutropenia and one G3 anaemia). One patient treated to cervical spine experienced G2 esophagitis, one patient treated to chest wall developed G3 skin toxicity. Overall the rate of G3 toxicity was 16.6%. No patient presented diarrhoea during radiotherapy, even those treated to radiotherapy sites close to small and large bowel. Pain significantly improved after radiotherapy (mean value NRS pre-RT=3.9, SD=3.07; mean value NRS after RT=0.9, SD= 0.46; p=<0.0001).

Conclusion Concomitant treatment of Abemaciclib and radiotherapy seems well tolerated showing acceptable toxicity.

PO-1271 Ultra-hypofractioned WBI in early stage breast cancer: a multicentric observational study

L. Di Lena 1 , I. Palumbo 2 , L. Rago 3 , G. Lazzari 3 , P. Anselmo 4 , M.C. De Santis 5 , M. Alessandro 6 , E. Perrucci 7 , G. Ingrosso 2 , A.G. Becchetti 1 , V. Bini 8 , C. Aristei 2