Abstract
BackgroundThe incidence of brain metastases in breast cancer (BCBM) patients is increasing. These patients have a very poor prognosis, and therefore, identification of blood-based biomarkers, such as circulating tumor cells (CTCs), and understanding the genomic heterogeneity could help to personalize treatment options.MethodsBoth EpCAM-dependent (CellSearch® System) and EpCAM-independent Ficoll-based density centrifugation methods were used to detect CTCs from 57 BCBM patients. DNA from individual CTCs and corresponding primary tumors and brain metastases were analyzed by next-generation sequencing (NGS) in order to evaluate copy number aberrations and single nucleotide variations (SNVs).ResultsCTCs were detected after EpCAM-dependent enrichment in 47.7% of the patients (≥ 5 CTCs/7.5 ml blood in 20.5%). The CTC count was associated with ERBB2 status (p = 0.029) of the primary tumor as well as with the prevalence of bone metastases (p = 0.021). EpCAM-independent enrichment revealed CTCs in 32.6% of the patients, especially among triple-negative breast cancer (TNBC) patients (70.0%). A positive CTC status after enrichment of either method was significantly associated with decreased overall survival time (p < 0.05). Combining the results of both enrichment methods, 63.6% of the patients were classified as CTC positive. In three patients, the matched tumor tissue and single CTCs were analyzed by NGS showing chromosomal aberrations with a high genomic clonality and mutations in pathways potentially important in brain metastasis formation.ConclusionThe detection of CTCs, regardless of the enrichment method, is of prognostic relevance in BCBM patients and in combination with molecular analysis of CTCs can help defining patients with higher risk of early relapse and suitability for targeted treatment.
Highlights
The incidence of brain metastases in breast cancer (BCBM) patients is increasing
Using this EpCAM-dependent method, ≥ 5 Circulating tumor cell (CTC)/7.5 ml blood were found in 9 patients (20.5%) and 1–4 CTCs/7.5 ml blood were found in 12 patients (27.3%) (Fig. 1); the median number of CTCs detected was 4 CTCs/7.5 ml blood
Among the ERBB2-positive cases, a very heterogeneous ERBB2 expression was seen: in one patient, one CTC was detected by ERBB2 expression while being negative for keratins; of two cases, all CTCs were positive for keratins but negative for ERBB2; two patients had keratin and ERBB2positive CTCs only; one case had five CTCs that were positive for keratin, but only two of them were positive for ERBB2; in two patients with an ERBB2-positive primary tumor, the single detected keratin-positive CTCs were found to be negative for ERBB2
Summary
The incidence of brain metastases in breast cancer (BCBM) patients is increasing. These patients have a very poor prognosis, and identification of blood-based biomarkers, such as circulating tumor cells (CTCs), and understanding the genomic heterogeneity could help to personalize treatment options. The incidence appears to be increasing over the last years, possibly as a result of better therapeutic options for the primary tumors and extracranial metastases [3]. Even after intensive multimodal therapy including resection and radiotherapy, brain metastases are correlated with a poor prognosis, consisting of a median survival time from diagnosis between 4 and 24 months [4, 5]. For this reason, novel and improved therapeutic approaches for BCBM patients are urgently needed. The molecular mechanisms leading to BCBM formation are still incompletely
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