Prognostic Significance of Disseminated Tumor Cells as Detected by Quantitative Real-Time Reverse-Transcriptase Polymerase Chain Reaction in Patients with Breast Cancer

Abstract

Background In this study we have validated the feasibility of detecting disseminated tumor cells (DTC) by real-time reverse-transcriptase polymerase chain reaction (RT-PCR) analysis. Bone marrow samples from a large cohort of patients with breast cancer were analyzed for the presence of DTC by immunocytochemistry (ICC) or a molecular-based method. Patients and Methods Bone marrow samples were collected from 170 patients with breast cancer with stage I-IV disease before the initiation of any local or systemic treatment. Staining for cytokeratin (CK)—positive cells was performed with the Epimet® kit. Disseminated tumor cells were also quantified by measuring relative gene expression for CK19 and mammaglobin (MAM) using a quantitative RT-PCR detection method. The mean follow-up time was 30 months. Kaplan-Meier analysis was used for predicting overall survival. Results Despite an excellent quantitative correlation and qualitative concordance between ICC and RT-PCR, survival analysis suggested an improved prognostic significance of DTC as detected by quantitative RT-PCR. Univariate survival analysis computed a relative risk of death of 2.87 for women with ICC-positive cells in the bone marrow, as compared with those without positive cells. The relative risk for women with RT-PCR—positive bone marrow was even higher: 3.5 (CK19) and 3.39 (MAM). In multivariate analysis, bone marrow CK19 was a stronger prognostic factor than bone marrow ICC. Conclusion Reversetranscriptase polymerase chain reaction—detected DTC is shown to be prognostically significant in untreated patients with breast cancer. Furthermore, it seems to be a more sensitive method for detecting DTC in bone marrow samples when compared with ICC.