Persistance of circulating tumor cells (CTCs) in peripheral blood of breast cancer (BC) patients two years after primary diagnosis

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Background: In metastatic BC, CTCs have shown to predict treatment efficacy and reduced survival. Recent data also indicate a potential prognostic relevance of CTCs after adjuvant chemotherapy. The SUCCESS trial evaluates the role of persisting CTCs two years after diagnosis in primary BC patients treated with zoledronate. Methods: We analyzed 23 mL of peripheral blood in N+ and high-risk N- primary BC pts receiving 3xFEC(500/100/500)-3xDoc100 q3w vs. 3xFEC(500/100/500)-3xDocgemcitabine (75/1000 d1+8) chemotherapy followed by 2 yrs (4mg q3mx24m) vs. 5 yrs (4mg q3mx24m followed by q6mx36m) of zoledronate. CTC results after two years are shown. CTCs were assessed with the CellSearchSystem (Veridex, Warren, USA). After immunomagnetic enrichment with an anti-Epcam-antibody, cells were labelled with anti-cytokeratin (8,18,19) and anti-CD45 antibodies. Pts were examined after a mean of 29 months (range 20–43). Results: The data of 579 pts two years after diagnosis are available. 4.3% of pts (n = 25) presented with >1CTC in peripheral blood. In pts with the detection of CTCs, the mean number of cells was 1 (range 1–29). While we found 1 CTC in 5.9% and 2 CTCs in 1.6% of pts, 1.5% had 3–5 CTCs, 1.2% >5 CTCs. The presence of >1CTC did not correlate with tumor size (p = 0.41), nodal status (p = 0.41), grading (p = 0.45), hormonal status (p = 0.92) or HER-2-Status of the tumor (p = 0.59). In this patient group, 9.7% and 6.9% of pts had presented with >1CTC at primary diagnosis and after chemotherapy, respectively. While the presence of CTCs at diagnosis was associated with CTCs after two years (p = 0.03), there was no correlation of CTCs after chemotherapy with the results at primary diagnosis (p = 0.08) or at two years (p = 0.23). In 184 postmenopausal HR+ pts endocrine treatment data was analyzed. CTCs at two years were detected in 6.8% of pts on tamoxifen (n = 9), while 1.9% of pts were positive on anastrozole treatment (n = 1; p = 0.19). Conclusions: CTCs persisting cytostatic, endocrine and zoledronate treatment, can be observed in a relevant number of clinically recurrence-free BC patients. Longer follow-up within the German SUCCESS study will give further insight in their prognostic relevance and show whether they can be used for real time tumor phenotyping or serve as treatment target.

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