Stereotactic radiosurgery for patients with breast cancer brain oligometastases - molecular subtypes and clinical outcomes

Abstract

Background: We sought to determine the clinical outcomes of patients with breast cancer (BC) who had undergone stereotactic radiosurgery (SRS) for a limited number of brain metastases (BM) and to identify factors influencing overall survival (OS) and local control.

Materials and methods: The records of 45 patients who underwent SRS for 72 brain lesions were retrospectively evaluated. Statistics included the chi-squared test, Kaplan-Meier method, and the multivariate Cox model.

Results: The median number of treated BM was 2 (range 1-10). Median OS from BM diagnosis and post-SRS were 27.6 [95% confidence interval (CI): 14.8-40.5) and 18.5 months (95% CI: 11.1-25.8), respectively. One-year and two-year survival rates after BM diagnosis were 55% and 41%, respectively. In a univariate analysis, the Luminal-B-human-epidermal-growth-receptor-positive (HER2+) subtype had the longest median OS at 39.1 months (95% CI: 34.1-44.1, p = 0.004). In an adjusted analysis, grade 2 [hazard ratio (HR): 0.1; 95% CI: 0.1-0.6, p = 0.005), craniotomy (HR: 0.3; 95% CI: 0.1-0.7; p = 0.006), and ≥ 2 systemic therapies received (HR: 0.3; 95% CI: 0.1-0.9, p = 0.028) were associated with improved OS. One-year and two-year intracranial progression-free survival rates were 85% and 63%, respectively. Four factors for a higher risk of any intracranial recurrence remained significant in the adjusted analysis, as follows: age < 50 years (HR: 4.2; 95% CI: 1.3-36.3; p = 0.014), grade 3 (HR: 3.7; 95% CI: 1.1-13.2; p = 0.038), HER2+ (HR: 6.9; 95% CI: 1.3-36.3; p = 0.023), and whether the brain was the first metastatic site (HR: 4.7; 95% CI: 1.6-14.5; p = 0.006).

Conclusion: Intrinsic BC characteristics are important determinants for both survival and intracranial control for patients undergoing SRS for oligometastatic brain disease.

Keywords: brain metastases; breast cancer; molecular subtype; radiation therapy; stereotactic radiosurgery.

Figure 1

Overall survival from brain metastases diagnosis by (A) Local treatment and (B) Breast cancer molecular subtypes. OS — overall survival; BM — brain metastases; SRS — stereotactic radiosurgery, WBRT — whole brain radiation therapy; TNBC — triple negative breast cancer; LUM A — luminal A; LUM B — luminal B; HER2 — human epidermal growth receptor