ESTRO 2024 - Abstract Book

S707

Clinical - Breast

ESTRO 2024

interval. Delayed surgery is crucial in higher PCR rates for early stage breast cancer after pre-operative radiation. Both radiation dose and time between radiation and surgery should be controlled in future studies.

Keywords: Pre-op radiation , stereotactic breast, S-PBI

2995

Digital Poster

Ablative Radiotherapy in Extracranial Oligometastatic Breast Cancer- a single institution experience

Filipa A Martins, Alice Alves, Catarina Elzen, Pedro Meireles, Gabriela Pinto

Centro Hospitalar Universitário São João, E.P.E., Radiotherapy, Porto, Portugal

Purpose/Objective:

Metastasis-directed ablative treatment in oligometastatic breast cancer is controversial, since the most recente clinical trials did not demonstrate a progression free survival or an overall survival benefit with local treatment. The patient and disease characteristics that determine a better response to local treatment are a subject of ongoing research. We aim to assess the group of patients who may benefit from local ablative radiotherapy to the oligometastases in breast cancer.

Material/Methods:

We conducted a retrospective analysis of 25 patients who received local ablative radiotherapy for extra-cranial oligometastatic breast cancer, between january 2014 and december 2022. Patient data, including age, cancer stage, metastatic sites, systemic and radiotherapy treatment, were collected. We evaluated time to progression and assessed the influence of clinical and treatment factors on outcomes. Toxicity was also evaluated.

Results:

Twenty-five patients were treated with ablative doses (conventional or stereotactic body radiotherapy) for a total number of 30 metastasis. The median age was 53 years (range 36-83) and a ECOG PS 0-1. Eighteen patients (72%) had metachronous and 7 (28%) synchronous lesions. Of noticed that 5 patients were treated for induced oligoprogression and 3 underwent subsequent treatment for another oligometastasis during the evaluated period. The luminal phenotype (40% A and 32% B) was the most frequent, with 8% HER-2+ and 20% Triple Negative (TN). Twenty one patients were treated to a single metastase, 3 patients treated simultaneously to 3 metastases and 1 patient treated to 2 metastases. Most frequent treated site was the bone in 60%, followed by pulmonar (28%), lymph node (8%) and liver (4%) metastases. Sixteen patients had systemic disease progression after a median of 21.6 months. After a median follow-up period of 28.7 months, 8 patients (89%) who did not show progression had only 1 lesion (6 bone and 2 lung) and 1 patient was treated for 3 bone lesions. The distribution between synchronous and metachronous lesions was similar (4 and 5 patients, respectively). Seven patients had luminal