ESTRO 2025 - Abstract Book

S549

Clinical - Breast

ESTRO 2025

References: 1. Buchholz TA, Ali S, Hunt KK. Multidisciplinary Management of Locoregional Recurrent Breast Cancer. J Clin Oncol. 2020;38(20):2321-8. 2. Clemons M, Danson S, Hamilton T, Goss P. Locoregionally recurrent breast cancer: incidence, risk factors and survival. Cancer Treat Rev. 2001;27(2):67-82. 3. Walstra CJEF, Schipper R-J, Poodt IGM, van Riet YE, Voogd AC, van der Sangen MJC, Nieuwenhuijzen GAP. Repeat breast-conserving therapy for ipsilateral breast cancer recurrence: A systematic review. European Journal of Surgical Oncology. 2019;45(8):1317-27.

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Digital Poster clinical value of bone radiotherapy in a prospective cohort of metastatic breast cancer treated with anti-cdk 4/6 Sofia Carrafiello 1 , Edy Ippolito 1 , Michele Fiore 1 , Sonia Silipigni 1 , Vincenzo Palumbo 1 , Francesco Pantano 2 , Giuseppe Casale 3 , Claudia Talocco 1 , Maria Grazia De Marinis 3 , Paolo Matteucci 1 , Sara Ramella 1 1 Radiation oncology, Fondazione policlinico campus Bio-Medico, Rome, Italy. 2 Medical oncology, Fondazione policlinico campus Bio-Medico, Rome, Italy. 3 Palliative care, Fondazione policlinico campus Bio-Medico, Rome, Italy Purpose/Objective: Cyclin-dependent kinase inhibitors (CDK4/6 inhibitors), combined with endocrine therapy, has become an established and efficient combination therapy in patients with advanced hormone receptor-positive breast cancer. Scientific evidence related to its combined used with RT, used for symptom palliation or local disease control, remains limited. The purpose of our study is to analyse the efficacy and safety of the combined use of CDK4/6 inhibitors and RT (both SBRT and non-SBRT) in term of pain management, using the Numerical Rating Scale (NRS) pre- and post-treatment, assess changes in analgesic therapy (categorized as stable, improved, or worsened), determine the impact of baseline and treatment factors on pain response, and analyze treatment-related toxicities (graded per CTCAE v5.0). Material/Methods: Patients with metastatic BC on RT and CDK4/6 inhibitors who consented to the COMBART study were eligible. Mean and SD values were used for continuous variables, counts and frequencies for categorical variables. Treatment related AEs collected were categorized and graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events (NCI CTCAE), version 5.0.1. Difference among groups were calculated by means of chi square test for categorical variables or T-Test for continuous variables Results: Our study included forty patients with advanced breast cancer concurrently treated with CDK4/6 inhibitors (palbociclib 30.8%, ribociclib 51.3%, abemaciclib 17.9%) and RT to a total of 131 metastatic lesions included, 30% were over 70 years old (with a mean G8 score of 13.8 ± 3.0) and 65% had no comorbidities, were all treated with baseline analgesics which included NSAIDs (51.2%), minor opioids (4.8%), and major opioids (17.6%). NRS scores pre- and post-treatement were analyzed, as a mean to assess overall pain reduction. We observed a significant reduction in the mean NRS (3.52 ± 2.98 to 1.31 ± 1.59 (p<0.01), with a mean percentage reduction of -45.7 ± 38.9%, particularly in patients treated with conventional RT treatments compared to SBRT (-58.6% vs. -39.9%; p=0.016). Radiological response, comorbidities and BED4 values showed no influence on the overall pain response. Also, Opioid users showed greater pain reductions than nonusers (p=0.049). For post-treatment analgesics therapy, stability was observed in 70.6% of patients, while it was improved in 14.3% and worsened in 10.3% of patients. Toxicity data are shown in table 1.