Abstract P1-12-09: Clinical characteristics of CNS metastases of different breast cancer subtypes – Results from a cohort study
Authors: Lindman H , Nilsson A , Gullbo J 
Published: March 2017

Abstract
Introduction: Secondary breast cancer in CNS is a rising clinical problem despite an ongoing improvement of the prognosis in breast cancer in general. The commonly proposed reason is the decreased passage through the blood-brain-barrier (BBB) of otherwise effective systemic therapies. The prognosis of patients (pts) with metastases (met) in CNS is poor and the therapy is mainly based on local therapy with surgery or stereotactic radiotherapy or alternatively, whole brain radiotherapy. However, therapy differs among centers and guidelines are based on relatively small studies with inhomogeneous groups of pts. The value of systemic therapy is not clearly established. Data has shown different outcome in different breast cancer subtypes.
Patients and Methods: Pts treated between 2009 and 2016 with metastases in CNS (brain, medulla and/or meningeal) were identified in our treatment database. This represents all breast cancer pts in Uppsala County with CNS involvement during that time period. We categorized the pts based on number of brain met and on the tumor subtype. We compared the pattern of metastases, the relationship to extra-CNS met and time, response to given therapy and survival.
Results: Of 68 pts 51% had oligometastases in brain, 41% multiple brain metastases and 7% meningeal metastases only. Median age was 58 years (range 34-81) median size of largest tumor was 16 mm. The most common subtype was HER2 positive (HER2) 37% followed by Luminal B (LumB) 31%, Triple negative (TNBC) 18% and Luminal A (LumA) 15%. The subtypes had different clinical appearance according to table:
HER2 (n=25)TNBC (n=12)LumB (n=21)LumA (n=10)Multiple met (&gt;3)44%9%48%60%Oligo met (1-3)56%91%38%30%Meningeal only0%9%14%10%Extra CNS met at diagnosis76%67%81%100%Median time from M1 to CNS met (months)302245Median survival (months)245.5146
In more than 50% of the TNBC pts was CNS the first site of disseminated disease. This was the case in only 24% of the LumB pts and none of the LumA pts. Systemic therapies were given to 91% of all pts and radiological complete responses in CNS were reported in 24% (HER2 32%, TNBC 17%, LumB 24% and LumA 10%). The median survival was 13 months, but differed significantly between the different subtypes and was surprisingly short for LumA, which not could be explained by death by metastases outside CNS. Eventually, developed 25% of all pts meningeal involvement. CNS met were the prime reason for death in 72% of the pts.
Conclusions: This cohort study describes the clinical appearance and prognosis of CNS metastases in breast cancer pts during a seven years period in the institution treating all pats in the County of Uppsala. Distinctive clinical differences between the breast cancer subtypes could be noticed which possible represents different mechanism in the metastatic process as well as different treatment response. The survival in the luminal subgroups was short and CNS met developed considerably later in the course of the disease when pts might have developed a more aggressive and therapy resistant disease.
Citation Format: Lindman H, Nilsson A, Gullbo J. Clinical characteristics of CNS metastases of different breast cancer subtypes – Results from a cohort study [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-12-09.