Abstract P1-01-06: Ki67-positive CTCs are associated with early disease relapse in patients with early breast cancer undergoing adjuvant chemotherapy

Abstract

Abstract Background: The determination of Ki67 in the primary tumor has prognostic value in early breast cancer (BC). We evaluated Ki67 expression in circulating tumor cells (CTCs) from patients with early BC undergoing adjuvant chemotherapy and correlated Ki67 positivity with patient outcome. Methods: Ki67 expression in CTCs was evaluated by immunofluorescent analysis in paired blood samples of patients with early BC (n=166) obtained before and after adjuvant chemotherapy. Ki67 expression was also evaluated in CTC-positive patients at 6 - 24 months after the end of chemotherapy (n=31). Cytospins of peripheral blood mononuclear cells were double stained with A45-B/B3 cytokeratin and Ki67 antibodies. The proliferation index (PI) of CTCs was defined as the ratio of Ki67-positive CTCs/total CTCs. Results: CTCs were detected in 53 (32%) patients before and/or after chemotherapy. Ki67-positive [Ki67(+)] CTCs were identified in 79% of CTC-positive patients, 25% presenting exclusively Ki67(+) CTCs and 21%, exclusively Ki67(-) CTCs. The mean value of Ki67(+) CTCs/patient remained unchanged pre- and post-chemotherapy [(mean±SE): pre- vs post-chemotherapy 2.5±0.7 vs 4.2±2, respectively; p= 0.900]. Similarly, the PI among the total CTCs detected pre- and post-chemotherapy was 59% and 60%, respectively. Ten (19%) of 53 CTC-positive and 9 (8%) of 113 CTC-negative patients relapsed (p = 0.039). In addition, all CTC-positive patients who relapsed harbored Ki67(+) CTCs before and/or after chemotherapy. Interestingly, 70% of them experienced early disease recurrence, ranging from 6-29 months after the initiation of adjuvant chemotherapy. Furthermore, 38.5% of patients with exclusively Ki67(+) CTCs relapsed compared to none among patients with exclusively Ki67(-) CTCs (p = 0.041). Of the 31 CTC-positive patients evaluated during follow-up, 39% remained CTC-positive. However, only 33.3% of them harbored Ki67(+) CTCs, 8.3% had exclusively Ki67(+) CTCs and 66.7% exclusively Ki67(-) CTCs. The mean value of Ki67(+) CTCs/patient was significantly reduced on the follow-up samples [(mean±SE): follow-up vs pre-chemotherapy, 1.35±1.3 vs 2.5±0.7, respectively; p=0.014 and follow-up vs post-chemotherapy, 1.35±1.3 vs 4.2±2, respectively; p= 0.026]. Conclusions: Ki67 expression on CTCs is predictive of early relapse in patients with early BC. Ki67 expression is not decreased by adjuvant chemotherapy, whereas it is reduced early during follow-up, possibly due to adjuvant hormone therapy and/or anti-HER2 therapy. The above results suggest that additional therapy is needed for patients with early BC and Ki67(+) CTCs to prevent early disease recurrence. Citation Format: Agelaki S, Spiliotaki M, Politaki E, Spanaki A, Kassiou L, Koinis F, Georgoulias V, Mavroudis D. Ki67-positive CTCs are associated with early disease relapse in patients with early breast cancer undergoing adjuvant chemotherapy [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P1-01-06.