Kitzmann, Kathleen

11095 Background: Biologic characterization of CTCs is increasingly important in determining metastatic breast cancer (MBC) patient (pt) prognosis and treatment prediction. Combined preliminary results from two earlier metastatic BC NCCTG trials, N0234 & N0336, suggested that the change in CTC mammaglobin (MGB1) gene expression between baseline and two cycles of chemotherapy predicted tumor response (p=0.04). The objectives of this study were to 1) determine CTC gene expression of CK19 and MGB1 before, during, and after treatment in N0436 & N0437 and 2) determine associations between baseline and post-treatment gene expression and treatment response. Methods: CTCs were enriched using CD45-depletion from ∼10ml EDTA blood obtained from metastatic BC pts before, after two cycles, and at end of treatment with either first/second-line irinotecan plus cetuximab (N0436) or first-line paclitaxel poliglumex and capecitabine (N0437). CK19 and MGB1 mRNA levels were determined using quantitative RT-PCR in baseline and serial CTC samples of up to 19 pts from N0436 and 40 pts from N0437. The relative gene expressions were normalized to β2-microglobulin and calibrated to healthy blood using the 2-ΔΔCt algorithm; a value of 2 was defined as positive for the respective marker. Results: CK19+ mRNA was detected in 58% of baseline samples from N0436 (11/19) and N0437 (23/40). MGB1+ mRNA was detected in 32% (6/19) and 38% (15/40) of N0436 and N0437 baseline samples, respectively. CK19+ mRNA was detected in 50% (7/14) and 56% (29/52) of N0436 and N0437 serial CTC samples, respectively. MGB1+ mRNA was detected in 29% (4/14) and 27% (14/52) of N0436 and N0437 serial CTC samples, respectively. Of the 66 serial samples, 27% of samples (18/66) had turned positive from baseline for CK19 or MGB1. CK19 mRNA was detected in 85% (33/39) of MGB1+ mRNA samples but their baseline mRNA levels were not correlated. Conclusions: CK19 mRNA was detected in MBC pts with similar frequencies to the CellSearch imaging system. CK19 was detected at a higher frequency than MGB1. In the majority of cases, MGB1 was co-expressed with CK19. Associations between gene expression and treatment response using Chi-Squared analyses and Cox regression models will be presented. No significant financial relationships to disclose.

Abstract Purpose: To investigate the associations between baseline and posttreatment circulating tumor cell (CTC) gene expression and outcome of patients enrolled in four North Central Cancer Treatment Group metastatic breast cancer (MBC) trials in which specimens were shipped (at 4°C) from community-based sites to a reference laboratory (Mayo Clinic, Rochester, MN). Experimental Design: Blood was collected at treating sites from MBC patients before (baseline), during, and at the end of treatment with erlotinib + gemcitabine (N0234), sorafenib (N0336), irinotecan + cetuximab (N0436), or paclitaxel-poliglumex + capecitabine (N0437). CTCs from 10 mL of EDTA blood were enriched with CD45 depletion, 24 to 30 hours postblood collection. Reverse transcription/quantitative PCR was used to determine cytokeratin-19 (CK19) and mammaglobin (MGB1) mRNA levels in CTCs from up to 13 (N0234), 16 (N0336), 18 (N0436), and 39 (N0437) patients. The gene expressions were normalized to β2-microglobulin and calibrated to healthy blood using the 2–ΔΔCq algorithm; positivity was defined as 2 or more. Results: CK19+mRNA cells were detected in 56% to 75% and MGB1+mRNA cells in 23% to 38% of 86 patients at baseline. CK19+mRNA cells were detected in 30% to 67% and MGB1+mRNA cells in 14% to 64% of 110 postbaseline serial samples. The presence of baseline CK19+mRNA cells (P = 0.01) but not MGB1+mRNA cells (P = 0.14) was significantly associated with shorter overall survival. A decrease in MGB1+mRNA levels (baseline-week 8) seemed to be associated with clinical response (P = 0.05). Conclusions: CTC gene expression analysis conducted by a reference laboratory is feasible when blood is collected from treating sites and processed 24 to 30 hours postcollection. The presence of baseline CK19+mRNA CTCs was associated with poor prognosis; a decrease in MGB1+mRNA CTCs may help predict response to therapy of MBC patients. Clin Cancer Res; 17(22); 7183–93. ©2011 AACR.

Abstract Purpose: We examined the feasibility of using molecular characterization of circulating tumor cells as a method for early detection of breast cancer. Research Design: Women without a prior history of cancer who had a breast abnormality detected on imaging followed by a breast biopsy were enrolled in this study. Density gradient centrifugation and immunomagnetic capture were used to enrich for epithelial cells from ∼20 mL of blood. Real-time reverse transcription-PCR was used to quantitate the expression levels of the highly breast-specific genes, mammaglobin, γ-aminobutyric acid type A receptor π subunit (GABA Aπ), B305D-C, and B726P in the epithelial cell–enriched samples. Results: The assay was technically feasible in 154 of 199 accrued patients. From their clinical assessment, 100 patients had benign breast disease, 10 patients had ductal carcinoma in situ, and 44 patients had invasive breast cancer. We constructed a diagnostic test that classified patients with mammaglobin levels of at least 32.2 copies/pg β-actin (units) in their circulating epithelial cells as positive for invasive breast cancer. This resulted in a sensitivity and specificity of 63.3% and 75.0%, respectively. A diagnostic test that classified patients as positive for invasive breast cancer when either mammaglobin levels were >46.3 units or B305D-C levels were >11.6 units increased the sensitivity and specificity to 70.5% and 81.0%, respectively. In the latter test, 12 of the 14 node-positive breast cancer patients were correctly identified. Including GABA Aπ and B726P in the test did not increase its diagnostic potential. Conclusions: These results suggest that molecular characterization of circulating epithelial cells using mammaglobin and B305D-C offers potential for early detection of invasive breast cancer.