P4-07-18: Prospective Assessment of Circulating Tumor Cells and Serum Markers for PFS Prediction in Metastatic Breast Cancer.

Abstract

Abstract Purpose: Circulating tumors cells (CTC) have been recently proposed as a new dynamic blood marker whose positivity at baseline is a prognostic factor and whose changes under treatment are correlated with progression-free survival (PFS) in metastatic breast cancer patients. However, serum markers levels are also used for the same purpose, and no clear comparison as been reported to date. Patients and methods: The IC 2006–04 enrolled prospectively 267 metastatic breast cancer patients treated by first line chemotherapy and confirmed that CTC levels are an independent prognostic factor for PFS and Overall survival (OS). A pre-planned endpoint was to compare prospectively the positivity rates and the value of CTC (CellSearch®), of serum tumor markers (CEA, CA 15–3, CYFRA 21.1), and of serum non-tumor markers (LDH, ALP) at baseline and under treatment for PFS prediction, independently from the other known prognostic factors, using univariate analyses and concordance indexes. Results: Table 1 shows the incidence of each of the 6 blood markers. Assessing all the 6 markers retrieved 90% of patients with at least one elevated marker at baseline. Interestingly, a combination of two markers (CA 15–3 and CYFRA 21.1, often used in lung cancer) retrieved 86% of patients with at least one marker elevated at baseline. All 6 markers were correlated with poor performance status, high number of metastatic sites and with each other. Each marker was associated, when elevated at baseline, with a significantly shorter PFS in univariate anlaysis. Serum marker changes during treatment, assessed either between baseline and week 3 or between baseline and week 6–9, were significantly associated with PFS, as reported for CTC. Concordance indexes comparison showed no clear superiority of any of the serum marker or CTC for PFS prediction. Conclusion: In the largest prospective CTC study in metastatic breast breast cancer, we previously reported that CTC count, but not serum markers, is an independent prognostic factor for PFS and overall survival. However, for the purpose of PFS prediction by measuring blood marker changes during treatment, currently available blood-derived markers (CTC and serum markers) had globally similar performances. Besides CEA and CA 15–3, CYFRA 21.1 is commonly elevated in metastatic breast cancer and has a strong prognostic value. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-07-18.