Circulating tumor cells: potential markers of minimal residual disease in ovarian cancer? a study of the OVCAD consortium

// Eva Obermayr 1 , Natalia Bednarz-Knoll 2 , Beatrice Orsetti 3, 4 , Heinz-Ulrich Weier 5 , Sandrina Lambrechts 6 , Dan Cacsire Castillo-Tong 1 , Alexander Reinthaller 1 , Elena Ioana Braicu 7 , Sven Mahner 8, 10 , Jalid Sehouli 7 , Ignace Vergote 6 , Charles Theillet 3, 4 , Robert Zeillinger 1, * and Burkhard Brandt 9, * 1 Department of Obstetrics and Gynecology, Medical University of Vienna, Vienna, Austria 2 Institute of Tumor Biology, University Medical Center Eppendorf, Hamburg, Germany 3 INSERM U1194, IRCM, Universite de Montpellier, Montpellier, France 4 Institut du Cancer de Montpellier, Montpellier, France 5 Department of Cancer and DNA Damage Responses, Life Sciences Division, University of California, Lawrence Berkeley National Laboratory, Berkeley, CA, USA 6 Division of Gynecological Oncology, Department of Obstetrics and Gynecology, Leuven Cancer Institute, University Hospitals Leuven, Katholieke Universiteit Leuven, Leuven, Belgium 7 Department of Gynecology, European Competence Center for Ovarian Cancer, Campus Virchow Klinikum, Charite - Universitatsmedizin Berlin, Berlin, Germany 8 Department of Gynecology and Gynecologic Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany 9 Institute of Clinical Chemistry, University Medical Center Schleswig-Holstein, Campus Kiel, Kiel, Germany 10 Department of Gynecology and Obstetrics, University of Munich, Munich, Germany * These authors contributed equally to this work Correspondence to: Burkhard Brandt, email: burkhard.brandt@uksh.de Keywords: circulating tumour cells; minimal residual disease; ovarian cancer; multi-marker analysis; FISH on CTCs Received: November 01, 2016      Accepted: October 11, 2017      Published: November 16, 2017 ABSTRACT Purpose: In 75% of ovarian cancer patients the tumor mass is completely eradicated by established surgical and cytotoxic treatment; however, the majority of the tumors recur within 24 months. Here we investigated the role of circulating tumor cells (CTCs) indicating occult tumor load, which remains inaccessible by established diagnostics. Experimental design: Blood was taken at diagnosis (baseline samples, n = 102) and six months after completion of adjuvant first-line chemotherapy (follow-up samples; n = 78). CTCs were enriched by density gradient centrifugation. A multi-marker immunostaining was established and further complemented by FISH on CTCs and tumor/metastasis tissues using probes for stem-cell like fusion genes MECOM and HHLA1. Results: CTCs were observed in 26.5% baseline and 7.7% follow-up blood samples at a mean number of 12.4 and 2.8 CTCs per ml blood, respectively. Baseline CTCs indicated a higher risk of death in R0 patients with complete gross resection (univariate: HR 2.158, 95% CI 1.111–4.191, p = 0.023; multivariate: HR 2.720, 95% CI 1.340–5.522, p = 0.006). At follow-up, the presence of CTCs was associated with response to primary treatment as assessed using RECIST criteria. Chromosomal gains at MECOM and HHLA1 loci suggest that the observed cells were cancer cells and reflect pathophysiological decisive chromosomal aberrations of the primary and metastatic tumors. Conclusions: Our data suggest that CTCs detected by the multi-marker protein panel and/or MECOM/HHLA1 FISH represent minimal residual disease in optimally debulked ovarian cancer patients. The role of CTCs cells especially for clinical therapy stratification of the patients has to be validated in consecutive larger studies applying standardized treatment schemes.