Abstract P4-12-30: Treatment outcomes of breast cancer liver metastasis treated with stereotactic body radiotherapy

Abstract

Abstract Background: To analyze the outcomes of breast cancer liver metastasis (BCLM) treated with stereotactic body radiotherapy (SBRT) and systemic treatment. Materials and methods: The treatment outcomes of 33 patients with oligometastasis (<5 metastases) at the time of liver metastasis (LM) or who became oligometastatic after systemic treatment were assessed. All of the metastases were diagnosed by 18-fluorodeoxyglucose positron emission computerized tomography (FDG-PET-CT). A total of 42 LM’s were treated with SBRT with a total of 54 Gy delivered in 3 fractions between April 2013 and April 2019. The local control (LC), overall survival (OS), and progression-free survival (PFS) rates were calculated using Kaplan-Meier analyses. Results: Median age and follow-up time were 45 years (range 24 - 77 years) and 13.6 months (range 1.9 - 59.4 months), respectively. Among 33 patients, 25 (76%) had solitary LM while 7 patients (21%) had two lesions and 1 patient (3%) had three lesions. Estrogen receptor (ER) and progesterone receptor (PR) were positive in 26 patients (79%) and 19 patients (58%), respectively. All patients had mastectomy for primary disease, and 29 patients (88%) received postoperative adjuvant chemotherapy and radiotherapy, while 4 patients (12%) had adjuvant chemotherapy only. Most of the patients [29 patients (88%)] developed LM during the follow-up of initial treatment, while only 4 patients (12%) had LM at the time of first diagnosis. 22 patients (67%) had another organ metastasis besides LM [lung 2 (6%), bone 13 (39%) and multiple 7 (21%)], only LM was observed in 11 patients (33%). At last visit, 21 patients (64%) had disease recurrence, median 8.0 months (range 0.7 - 30.6 months) after completion of liver SBRT. Only 2 patients (6%) had local recurrences and 19 patients (58%) had distant disease recurrence. Median OS and PFS were 35 months [95% confidence interval (CI) 9.9 - 60.1 months]) and 10.4 months (95% CI; 8.1 - 12.6 months), respectively. The 1- and 2-year LC and OS rates were 90% and 60%, respectively. In uni- and multivariate analysis, no significant prognostic factors, including disease extension, size of metastasis, number of liver metastasis and timing of liver metastasis, hormonal status affecting survival and local control were found. No patients experienced Grade 4 or 5 toxicity; furthermore, only two patients experienced rib fracture 6-8 months after completion of treatment, and one patient had a duodenal ulcer. Conclusion: This study is the first to evaluate the feasibility of SBRT to BCLM patients in a larger patient cohort. Our findings support that the liver SBRT is a feasible and safe method for BCLM with excellent LC and acceptable toxicities. Keywords: Breast cancer, Liver metastasis, Radiotherapy, Stereotactic body radiotherapy, Survival Citation Format: Ozan Cem Guler, Berna Akkus Yıldırım, Ozgur Ozyilkan, Cem Onal. Treatment outcomes of breast cancer liver metastasis treated with stereotactic body radiotherapy [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-30.