Multicenter study on the detection of disseminated tumor cells in primary breast cancer.

Abstract

Abstract Abstract #5021 Background: Detection of disseminated tumor cells (DTC) in bone marrow (BM) has prognostic value in primary breast cancer (BC) and is currently under investigation for therapy stratification and monitoring. Anti-cytokeratin (CK) antibodies (Abs) have been established as markers for detection of such DTC in patients with BC. Here we present a direct comparison of the two Abs most frequently used for DTC detection over the past 10 years.
 Material and Methods: We screened BM samples from 391 BC patients of which 64 were node-positive (N+). All patients were free of any signs of overt metastases (stage M0, pT1-3, pN0-3). Tumor cells in BM were enriched by Ficoll-Hypaque gradient and the mononuclear cell (MNC) fraction was spun on slides. For each patient 2*106 MNC were analyzed per Ab, using A45-B/B3 (A45) and AE1/AE3 (AE) Abs in parallel. A45 staining was, however, performed a couple of years later than AE staining, on cytospins stored at -80°C. All samples were screened automatically for the presence of CK-positive cells. By morphological evaluation only TC-compatible cells were scored positive. Median follow-up times ranged from 5 to 118 months.
 Results: For both Abs, the number of DTC revealed was 5 or less. Of the 391 patients, 24 patients (6.1%) were positive for A45, and 41 patients (10.5%) for AE, respectively. Concordance obtained by cross-analysis for the two Abs was 84.4%, whereas the overlap in positive cases was only 3.2%. Regarding immunohistopathological characteristics AE- and A45-positive BM were found significantly more frequent in tumors of higher nodal status (p=0.003 and p=0.026), and for AE also in hormone receptor negative (HR-) compared to HR+ patients (p=0.006). Positivity for AE and/or A45 staining in BM correlated with high nodal status and large tumor size (p=0.001 and p= 0.016, respectively). Survival analyses revealed shorter relapse-free survival for A45-positive patients (p=0.026). In node-positive patients, a significantly worse prognosis regarding overall and BC specific survival was observed for AE-positive (p=0.0245 and p=0.0125) and for AE- and/or A45-positive patients (p=0.035 and p=0.044, respectively). In node-negative patients, A45-positivity was correlated to a significantly shorter relapse-free survival (p=0.032). Immunocytochemical double staining of BM samples from 26 patients (M+ and M0) revealed subpopulations of DTC labeled with both Abs (in 8/26 cases) and other DTC exclusively stained for either A45 or AE (4/26).
 Discussion: Our results indicate that the two anti-cytokeratin Abs most frequently used for DTC detection in BM do not give identical results. They appear to identify at least partially different subpopulations of DTC in BC patients. This implies a possible advantage of the combined use of these Abs in future trials using DTC diagnostics. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5021.