ESTRO 2024 - Abstract Book

S548

Clinical - Breast

ESTRO 2024

Italy. 5 Azienda USL Toscana Sud Est, Radiation Oncology Unit of Arezzo and Valdarno, Arezzo and Montevarchi, Italy. 6 Azienda Ospedaliera Universitaria delle Marche, Radiotherapy Department, Ancona, Italy. 7 IRCCS Humanitas Research Hospital, Radiotherapy and Radiosurgery Department, Rozzano, Milano, Italy. 8 University of Perugia and Perugia General Hospital, Radiation Oncology Section, Perugia, Italy

Purpose/Objective:

The present review investigates the impact on metastasis local control and tolerability of different therapeutic approaches (Stereotactic Brain Radiotherapy (SBRT), Whole Brain Radiotherapy (WBRT), Metastasectomy and Surgery plus Tumor Bed RT) for brain metastases (BM) in HER2 metastatic breast cancer (BC) patients (pts). The aims were to enhance knowledge and define the best therapeutic choice for limited (<3 BM) and multiple BM.

Material/Methods:

A systematic review according to PRISMA methodology was performed. A literature search via PICO in MEDLINE/PubMed database was conducted in February 2023. The following keywords were used with different arrangements: (P) her2 metastatic BC/ metastatic BC, (I) SBRT/ surgery plus RT / brain surgery and RT, (C) brain surgery/surgery alone/brain metastasectomy/ WBRT, (O) local control and toxicity. Clinical trials enrolling pts aged >18 years, affected by HER2 metastatic BC and suitable for local BM treatments with/without systemic therapies were specifically included. Analysis of bias of included studies was performed according to the Evidence Project Risk of Bias tool. The primary outcomes were local control (LC) and toxicity; data on survival outcomes were also collected. A total of 576 studies were identified. No randomized controlled trials comparing the investigated approaches were founded. Studies were grouped according to the proposed therapeutic options and a specific analysis for reirradiation studies was performed. After the PRISMA-based study selection, a total of 19 retrospective studies were included in a qualitative synthesis. A main exclusion criteria was no available data on HER2 BC pts. 15 studies reported on pts treated with SBRT, 5 studies discussed on reirradiated pts (also including SBRT), 4 studies analyzed the impact of tumor bed RT, 5 studies reported on WBRT (both in exclusive and reirradiation setting). A variety of SBRT fractionations schedules (according to BM number-site-dimension) and RT techniques (i.e. Gamma Knife, VMAT) were observed among the analyzed studies. 16 papers reported on survival data but only 8 studies (SBRT group) assessed LC and its surrogated parameters (i.e. local failure, freedom from local recurrence, complete response/local progression). High rate of LC was reported at 1 year after SBRT (up to 90% among studies evaluating BC pts also including HER2; up to 73-75% in 2 studies specifically analyzing HER2 pts). No response at 6 months was observed in a single study with small sample size (6 HER2 pts). The use of anti-HER-2 agents improved LC in 2 studies. Radionecrosis was assessed in 6 SBRT studies and in one study on reirradiation; other neurological toxicities were observed in 3 studies (1 SBRT, 1 reirradiation, 1 WBRT). Results:

Conclusion:

Despite the limitations of this literature review (no prospective data, no comparison arms, limited data on HER2 metastatic BC pts), the encouraging rates of BM LC combined with satisfactory toxicity outcomes of SBRT may support the use of this modern approach for HER2 BC pts, especially in the era of personalized medicine - with new