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Introduction

Traditional factors currently used for prognostic stratification do not always predict adequately treatment response and disease evolution in advanced breast cancer patients. Therefore, the use of blood-based markers, such as circulating tumor cells (CTCs), represents a promising complementary strategy for disease monitoring. In this retrospective study, we explored the role of CTC counts as predictors of disease evolution in breast cancer patients with limited metastatic dissemination.

Methods

492 advanced breast cancer patients who had a CTC count assessed by CellSearch prior to starting a new line of systemic therapy were eligible for this analysis. Using the threshold of 5 cells/7.5mL of blood, pretreatment CTC counts were correlated in the overall population with metastatic site distribution, evaluated at baseline and at the time of treatment failure, using the Fisher's Exact test. Time to visceral progression, as well as, time to the development of new metastatic lesions and sites were estimated in patients with non-visceral metastases and with single-site metastatic disease, respectively, by the Kaplan-Meier method. Survival times were compared among groups according to pretreatment CTC count by log-Rank test.

Results

In the overall population, pretreatment CTCs were associated with increased baseline number of metastatic sites, compared with CTCs (P=.0077). At the time of treatment failure, patients with CTCs developed more frequently new metastatic lesions and sites compared to those with CTCs <5 (development of new lesions P=.0002; development of new sites P=.0031). Among patients with disease originally confined to non-visceral sites, CTCs were associated with remarkably shorter time to visceral metastases (P=.0021) and overall survival (P=.0006), compared with CTCs. Finally, in patients with single-site metastatic disease, CTCs were associated with a significant reduction of the time to development of new metastatic sites (P=.0051) and lesions (P=.0002), and with worse overall survival (P=.0101).

Conclusion

Our results suggest that baseline CTC counts can be used as an early predictor of metastatic potential in breast cancer patients with limited metastatic dissemination.


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