Abstract P4-01-12: Circulating tumor cells (CTC) and endothelial cells (CEC) changes in HER2 negative metastatic breast cancer (MBC) patients treated with first line weekly paclitaxel and bevacizumab: Preliminary results of a prospective cohort from the French Breast Cancer

Abstract

Abstract Background: increased levels of circulating tumor cells (CTC) are associated with worse progression-free survival (PFS) and overall survival (OS) in patients (pts) with MBC (Bidard FC et al, Lancet Oncol 2014). The failure of chemotherapy to reduce CTCs to levels below five CTCs per 7.5 mL whole blood at first follow-up after initiating a new systemic therapy for MBC predicts shorter time to progression and OS. It has been hypothesized that bevacizumab could modify CTC prognostic value due to extravasation or epithelio-mesenchymal transition induction. CEC variations to predict benefit of anti-angiogenic treatment is still controversial. Patients & methods: the French cohort COMET is a prospective study including first line HER2 negative pts receiving weekly paclitaxel and bevacizumab according to EMEA approved combination. The aim of this cohort is to evaluate clinical, biological and radiological parameters associated with pts outcome (CTC, CEC, VEGFA levels, ctDNA, pharmacogenomic polymorphisms, metabolomic parameters, visceral fat assessed by initial CTscan, serum estradiol level, and quality of life). We present here the first planned analysis on 206 patients evaluated for CTC and CEC using the FDA cleared CellSearch method. Results: inclusions started in 09/2012. At time of analysis, 219 patients were included, 211 were evaluable for CTC at baseline (failure rate 4%) and 207 for CEC at baseline (failure rate 5%). Due to short follow-up, 173 pts and 166 pts were evaluable for both CTC and CEC at baseline and first day of second cycle of CT (D1C2) respectively. At baseline, 100/211 (47%) pts had ≥ 5 CTC (median 4 (range 0-30,000) and 30% had no detectable CTC (0 CTC). After one cycle of chemotherapy (D28) 38 pts (22%) had still ≥ 5 CTC: 37 pts with initial high level and only one patient with low CTC at baseline had increased CTC above 5. Median number CEC was 21 (0)-2231) at baseline and 22 (1-881) at D1C2. CEC increased in 16% and decreased in 15% of the cases. CTC & CEC changes after one cycleCTC BaselineCTC at D1C2CEC BaselineCEC at D1C2≥ 5≥ 537 (21%)>20>2065 (39%)≥ 5<545 (26%)>20≤ 2025 (15%)<5≥ 51 (<1%)≤ 20>2027 (16%)<5<590 (52%)≤ 20≤ 2049 (30%)Total173166 CTC number at baseline line and CTC D1C2 were correlated (p<0.01) (Spearman test). There was no correlation between CEC at baseline or at D1C2 with CTC or CTC changes. Final analysis will be completed when 206 couples for both CTC and CEC at baseline and D1C2 will be available. Accrual is still ongoing. Conclusion: this 22% rate of failure to reduce CTC < 5 after one cycle of first line CT in a homogeneously bevacizumab-treated cohort of MBC patients did not differ from previous series. As second lines of chemotherapy do not improve the poor prognosis of this group of patients according to the SWOG 500 study results (Smerage et al, JCO 2014), trials of novel therapeutic agents should be considered at the time of progression. Citation Format: Jean-Yves Pierga, Isabelle Vaucher, Maya Gutierrez, Olivier Tredan, Séverine Guiu, Gilles Romieu, Anthony Goncalves, Marc Debled, Christelle Levy, Jean-Marc Ferrero, Christelle Jouannaud, Elisabeth Luporsi, Marie-Ange Mouret-Reynier, Florence Dalenc, Bernard Asselain, Jerome Lemonnier, Francois-Clement Bidard. Circulating tumor cells (CTC) and endothelial cells (CEC) changes in HER2 negative metastatic breast cancer (MBC) patients treated with first line weekly paclitaxel and bevacizumab: Preliminary results of a prospective cohort from the French Breast Cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P4-01-12.