Abstract GS4-08: Clinical utility of repeated circulating tumor cell (CTC) enumeration as early treatment monitoring tool in metastatic breast cancer (MBC) - a global pooled analysis with individual patient data

Background:

Several studies suggest clinical utility of serial circulating tumor cell (CTC) enumeration as a means of assessing response status in metastatic breast cancer (MBC). The aim of this study is to conduct a comprehensive pooled analysis comprising globally available data to further define and explore the role of CTC enumeration as a tool for early treatment monitoring in patients with MBC with a focus on the predictive power in different breast cancer subtypes and clinical settings.

Methods:

In a global effort, peer-reviewed published studies with data on repeated CTC assessments (CellSearch® technology; Menarini Silicon Biosystems; Bologna, Italy) in MBC patients were screened and investigators were asked to provide individual patient data for this pooled analysis. 2761 cases from 32 data sets with data on both baseline and one follow up CTC assessments were included in the analysis (median time interval between the two CTC assessments 35 days). Data were analyzed using log rank tests and Cox regressions to evaluate the association between serial CTC enumeration results and overall survival (OS) in the full patient cohort and defined subgroups.

Results:

588 (21.3%) patients had no CTCs at both time points (neg/neg), 236 (8.5%) patients were CTC negative at baseline and CTC positive at follow up (neg/pos), 712 (25.8%) patients converted from CTC positive at baseline to CTC negative (pos/neg), and 1225 (44.4%) patients had at least one CTC at both time points (pos/pos). Log rank tests showed significant differences in OS between these four CTC change groups (p < 0.0001 for all pairwise comparisons except for the comparison between neg/pos and pos/neg, p = 0.015). Median OS for the neg/neg, neg/pos, pos/neg and pos/pos group was 45.6, 26.1, 34.6, and 17.6 months, respectively. Hazard ratios (HR) (reference group neg/neg) were 1.38 (95% CI 1.16 - 1.64) for the pos/neg group, 1.78 (95% CI 1.43 - 2.22) for the neg/pos group, and 3.06 (95% CI 2.63 - 3.56) for the pos/pos group. Results were similar if a cutoff of 5 CTCs was used for CTC positivity (pos/neg group: HR 1.43, 95% CI 1.25 - 1.63; neg/pos group: HR 2.39, 95% CI 1.91 - 2.99; pos/pos group: HR 3.54, 95% CI 3.12 - 4.02).

In total, 2586 patients could be assigned to different tumor subtypes based on known hormone receptor (ER) and HER2 status of the primary tumor: 1513 (58.5%) patients had a luminal-like tumor (ER positive, HER2 negative), 682 (26.4%) patients had a HER2-positive tumor, and 391 (15.1%) patients had a triple-negative tumor. In patients with luminal-like tumors, the hazard ratios were 1.67 (95% CI 1.29 - 2.17), 2.01 (95% CI 1.45 - 2.77), and 3.87 (95% CI 3.09 - 4.83) for the pos/neg, neg/pos, and pos/pos group, respectively. In patients with HER2-positive tumors, the neg/pos group (HR 1.68, 95% CI 1.12 - 2.53) and the pos/pos group (HR 2.11, 95% CI 1.58 - 2.83) showed significantly worse OS compared to the neg/neg group, while in triple-negative patients, the pos/pos group had a significantly shorter OS compared to the neg/neg group (HR 2.99, 95% CI 2.11 - 4.24).

The results will be up-dated by inclusion of additional large data sets (CALGB 40502, CALGB 40503, COMET, SWOG S0500, TBCRC 001) for the analysis to be presented at SABCS 2020.

Conclusion:

This large pooled analysis confirms that at a median of 35 days after treatment initiation, follow-up CTC assessments strongly predict overall survival. These results suggest potential clinical utility of CTC monitoring as early response marker in MBC, especially in luminal-like tumors.

Citation Format: Wolfgang J Janni, Tracy C. Yab, Daniel F. Hayes, Massimo Cristofanilli, Francois-Clement Bidard, Michail Ignatiadis, Meredith M. Regan, Catherine Alix-Panabières, William E. Barlow, Carlos Caldas, Lisa A. Carey, Luc Dirix, Tanja Fehm, Jose A. Garcia-Saenz, Paola Gazzaniga, Daniele Generali, Lorenzo Gerratana, Rafael Gisbert-Criado, William Jacot, Zefei Jiang, Evi Lianidou, Mark J.M. Magbanua, Luis Manso, Dimitrios Mavroudis, Volkmar Müller, Elisabetta Munzone, Klaus Pantel, Jean-Yves Pierga, Brigitte Rack, Sabine Riethdorf, Hope S. Rugo, Kostandinos Sideras, Stefan Sleijfer, Jeffrey Smerage, Justin Stebbing, Leon W.M.M. Terstappen, José Vidal-Martínez, Rita Zamarchi, Karthik Giridhar, Thomas W.P. Friedl, Minetta C. Liu. Clinical utility of repeated circulating tumor cell (CTC) enumeration as early treatment monitoring tool in metastatic breast cancer (MBC) - a global pooled analysis with individual patient data [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr GS4-08.

Abstract P2-01-01: Trajectory patterns of circulating tumor cells (CTC) in chemotherapy-treated metastatic breast cancer (MBC) patients predict poor clinical outcomes: CALGB 40502 (Alliance)/NCCTG N063H study

Little is known about the dynamics of CTCs during treatment and its clinical significance. We examined the predictive utility of serial CTC analysis in ER+HER2- MBC patients (pts) treated with chemotherapy in the CALGB 40502/NCCTG N063H study, a randomized phase III trial of weekly paclitaxel compared to weekly nanoparticle albumin bound nab-paclitaxel or ixabepilone +/- bevacizumab as first-line therapy (ClinicalTrials.gov Identifier: NCT00785291, Support: U10CA180821, U10CA180882).

Methods: Of the 783 pts treated, 469 had ≥3 serial blood samples (including baseline) successfully analyzed for CTCs by CellSearch® and were included in this analysis (n=2,202). Samples with ≥5 CTCs per 7.5 mLs of blood were considered CTC+. The prognostic and predictive performance of baseline CTCs (bCTC) and CTC status from baseline to cycle 2 (b2CTC) were compared to a novel latent mixture model classification based on trajectory of CTCs (tCTC). Akaike Information Criterion (AIC) was used to select the model (bCTC vs b2CTC vs tCTC) that best predicts overall survival (OS), progression-free survival (PFS), and time-to-treatment failure (TTF).

Results: 53% of the pts were CTC+ at baseline. b2CTC status changed in 36% of the pts, most of whom were CTC+CTC- (35%), and very few CTC-CTC+ (1%); the rest of the pts did not experience a change in b2CTC status (46% CTC-CTC- and 19% CTC+CTC+). Mixture model analysis revealed 4 groups of pts that show distinct tCTC patterns over the course of treatment: consitently very low/undectectable CTCs (tCTCneg, 56%), low (tCTClo, 24%), intermediate (tCTCmid, 15%), or high (tCTChi, 5%). bCTC, b2CTC, and tCTC were significantly correlated with tumor subtype (all p <0.0022) and presence of bone metastasis (all p <0.0001). Multivariate analysis showed that pts who were CTC+ at baseline, and those whose b2CTC status remained positive (CTC+CTC+) had significantly reduced OS, PFS and TTF.

 OSPFSTTFModelsHR (95% CI)p-valueHR (95% CI)p-valueHR (95% CI)p-valuebCTC (vs CTC-)      → CTC+2.5(1.8-3.3)<0.00011.6(1.3-2.0)<0.00011.3(1.1-1.6)0.0046b2CTC (vs CTC+CTC-)      → CTC-CTC+1.6(0.5-5.4)0.41491.6(0.6-4.5)0.39051.6(0.6-4.3)0.3961→ CTC+CTC+2.7(1.9-3.8)<0.00011.8(1.4-2.5)<0.00011.8(1.3-2.4)<0.0001→ CTC-CTC-0.5(0.4-0.8)0.00020.8(0.6-0.9)0.01600.9(0.7-1.1)0.2771tCTC (vs tCTCneg)      → tCTClo2.6(1.9-3.7)<0.00011.9(1.4-2.4)<0.00010.9(0.7-1.1)0.0033→ tCTCmid5.3(3.6-8.0)<0.00012.5(1.8-3.4)<0.00011.8(1.4-2.5)0.0001→ tCTChi10.8(6.1-19)<0.00013.0(1.8-5.0)<0.00012.3(1.4-3.7)0.0009CTC- (<5 CTCs per 7.5 mLs); CTC+ (≥5 CTCs per 7.5 mLs)

Pts with tCTClo, tCTCmid and tCTChi had significantly shorter OS, PFS and TTF compared to those with tCTCneg. After adjustment for potential confounders, AIC analysis revealed that the tCTC model best predicts OS and PFS, while b2CTC best predicts TTF.

 AIC Score*ModelsOSPFSTTFbCTC243240514199b2CTC240540384186tCTC237940264188*The lowest AIC score indicates the best model.

Conclusions: Analysis of CTC trajectory patterns identified pts with poor outcome who could potentially benefit from more effective treatment. Validation in independent cohorts is warranted to confirm the findings in this study.

Citation Format: Magbanua MJ, Hendrix L, Hyslop T, Barry WT, Winer EP, Hudis C, Toppmeyer D, Burnstein H, Qadir M, Ma C, Scott JH, Park JW, Rugo HS. Trajectory patterns of circulating tumor cells (CTC) in chemotherapy-treated metastatic breast cancer (MBC) patients predict poor clinical outcomes: CALGB 40502 (Alliance)/NCCTG N063H study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P2-01-01.

P4-07-17: Isolation of Highly Pure Circulating Tumor Cells (CTCs) from Metastatic Breast Cancer (MBC) Patients for Gene Expression Analysis

Background: The paucity of information regarding the molecular nature of CTCs can be largely attributed to the difficulty of isolating these rare cells. As such, efforts on RNA profiling of CTCs have been limited to studies using immuno-enriched samples containing a high background of leukocytes.

Methods: We developed a two-step process: immunomagnetic enrichment followed by fluorescence activated cell sorting (IE/FACS) to isolate CTCs away from leukocytes and performed expression analysis on a limited panel of genes. Magnetic beads coated with EpCAM mAb were used to enrich for tumor cells. Enriched samples were then subjected to FACS using fluorescently labeled mAbs to distinguish tumor cells (EpCAM+) from leukocytes (CD45+) during sorting. CTCs and matched leukocytes were isolated from 67 sequential patients with MBC. Total RNA from isolated 20–50 cells was reverse-transcribed into cDNA. Sixty four (64) CTC-related genes from previous published reports were chosen for expression analysis. cDNA of these genes were pre-amplified and analyzed in triplicate via Taqman®-based RT-PCR in a low density array format. Statistical analysis of gene expression data was performed using Realtime Statminer®.

Results: Unsupervised hierarchical clustering analysis showed that CTCs clustered away from the leukocytes. Differential gene expression analysis revealed the up-regulation of several genes including EPCAM, MUC1, and KRT19 in CTCs (adjusted p <0.05). In addition, CTCs showed a significant down-regulation of the leukocyte-specific marker PTPRC (CD45) as well as CD44 and VIM, markers associated with stem cellness and epithelial to mesenchymal transition, respectively.

Discussion: We demonstrate the feasibility of isolation and gene expression analysis of CTCs. Molecular profiling confirmed that isolated CTCs were highly pure with little or no evidence of leukocyte contamination. This approach can serve as a non-invasive source of tumor tissue for further molecular characterization of CTCs and for monitoring of therapeutic efficacy of targeted therapies in clinical trials. This study was supported by CALGB and BCRF.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-07-17.