ESTRO 2023 - Abstract Book

S893

Digital Posters

ESTRO 2023

1 University of Palermo, radiation oncology school, Palermo, Italy; 2 ARNAS Civico hospital, radiotherapy unit, Palermo, Italy; 3 ARNAS Civico hospital, department of neuroradiology, Palermo, Italy; 4 ARNAS Civico hospital, neurosurgery unit, Palermo, Italy; 5 Arnas Civico hospital, medical oncology unit, Palermo, Italy Purpose or Objective The role of stereotactic radiotherapy (SRT) for the treatment of brain metastases is well consolidated and supported by high level evidence in the literature. In the present study we report the outcomes of our mono-institutional experience of Helical Tomotherapy (HT)-based SRT for brain metastases. Materials and Methods This study reports data collected from a retrospective series of patients with brain metastases treated with HT-SRT. Inclusion criteria were: KPS>70; life expectancy>6 months; ≤ 5 brain metastases; limited uncontrolled extracranial disease (up to 3 body metastases). Survival endpoints were assessed using Kaplan-Meier method and Cox regression for uni- and multi-variate analyses. Graphpad Prism was used for statistical analysis. Toxicity was prospectively collected using the CTCAE v5.0 criteria. Results From March 2018 to June 2022 a total of 64 lesions in 37 patients was treated with HT-SRT for a median total dose of 30 Gy (range, 28-30) in a median number of fractions of 5 (3-5). Median PTV was 2.66 cc (0.74-30.69cc). The most frequent primary histologies were NSCLC, colorectal cancer and breast cancer, respectively in 54%, 13.6% and 16.2%. Concurrent systemic therapy was administered in 56% of patients. With a median follow-up of 7 months (3-38), 1- and 2-years local control (LC) rates were 92,5% and 92,5%; at multivariate analysis, higher RT doses were predictive of improved LC (p=0.013). Similarly, higher RT doses were related to improved intracranial progression-free survival (IPFS) rates, although not reaching statistical significance. At multivariate analysis, LC was correlated to a better IPFS (p=0,01). Global IPFS rates were 56,75% and 51,35% at 1- and 2-years. Systemic progression-free survival rates were 51,35% and 48,64% respectively, without any predictive factor for improved outcomes at multivariate analysis. Overall survival (OS) rates were 54,05% and 40,54%, with uncontrolled extracranial disease and low RT doses related to worse survival outcomes. No severe adverse event reported. Conclusion HT-SRT resulted in promising initial results. Interestingly, higher RT doses showed statistical significance for improved outcomes in terms of LC and OS. 1 Centro di riferimento oncologico, Oncologia radioterapica , Aviano, Italy; 2 Centro di riferimento oncologico, Oncologia radioterapica, Aviano, Italy Purpose or Objective Patients with HER2 over-expressed breast cancer were at higher risk to develop brain metastases in comparison to other histotypes. The aim of our study is to investigate if HER2 status correlates also with brain metastases (BM) distribution, intracranial disease control and prognosis after radiation therapy Materials and Methods Patients included in this mono-institutional retrospective cohort received radiation therapy for breast cancer BM during the last 5 years. Medical charts and contrast enhancement brain MRI images were reviewed. Patients with resected or limited ( ≤ 4 lesions) BM were treated with focal stereotactic radiation therapy (21Gy/1 fraction or 18-27Gy/3 fractions or 25-30Gy in 5 fractions ), while patients with multiple brain metastases (>4 lesions) received WBRT (20Gy/5 fractions or 30Gy/10fr). Intracranial distribution of brain metastases before radiotherapy were correlated with HER2 status. Intracranial progressive disease was defined according RANO-BM criteria. Intracranial disease control and overall survival (OS) in HER2 positive and HER2 low/negative patients were estimated with Kaplan Meyer method and compared with log rank test Results A total of 71 patients were identified. Five patients were lost at follow up and data from 66 patients were analyzed. Median follow up was 9 months (range: 0-57 months). Breast cancer were categorized as HER2 enriched and HER2 low/negative in 26 (39%) and 40 (61%) of cases, respectively. A total of 400 BM were identified on MRI before radiotherapy and were located in cerebral lobes (63%), cerebellum (31%), basal ganglia (5%), and brainstem (1%). Cerebellum involvement is more frequent in HER2 enriched tumours (42/107 BM, 39%) that in HER2 low/negative (82/293 BM, 28%), p=0.03. BM were categorized as limited in 39 (59%) patients and as multiple in 27 (41%). One-year intracranial disease control was 43% vs. 23% (p=0.02) in HER2 enriched and HER2 low/negative group respectively. A second course of radiotherapy was delivered after intracranial progression in 28 cases (42%). One-year OS was 61% vs. 39% (p=0.003) for HER2 enriched and HER2 low/negative, respectively. The survival advantage for HER2 enriched group was evident for limited metastases (median OS: 52 months in HER2 enriched vs. 12 months in HER2 low/negative, p=0.02) but not for multiple metastases (median OS: 10 months in HER2 enriched vs. 6 months in HER2 low/negative, p=NS) PO-1117 HER2 expression correlated with intracranial control and prognosis of breast cancer brain metastases A. Caroli 1 , A. Revelant 2 , F. Bertini 2 , F. Gessoni 1 , L. Vinante 2

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