Evaluation of proliferation and apoptosis markers in circulating tumor cells (CTCs) of women with early breast cancer who are candidates for tumor dormancy.

Abstract

e22101 Background: Clinical dormancy is frequently observed in breast cancer (BC). In the present study, we aimed to characterize CTCs in dormancy candidates (DC) with BC in terms of proliferation and apoptosis. Methods: Cytospins of peripheral blood mononuclear cells (PBMCs) were obtained from DC (n=122) disease-free for ≥5 yrs and from metastatic pts (n=37) on relapse that occurred ≥5 yrs after surgery. Sequential samples (n=27) of 8 DC with late relapse and from 8 relapse-free (n=38), were also analyzed. 106 PBMCs were stained with pancytokeratin antibody along with ki-67 and M30 as proliferation and apoptosis markers, respectively. Results: CTCs were identified in 40 (32%) of 122 DC. In 25 (61.5%), all CTCs were ki-67(-)/M30(-), 7 (17.5%) had ki-67(+), 4 (10%) M30(+) CTCs and 4 had both phenotypes. Among 243 CTCs detected, 201 (82.5%) were ki-67(-)/M30(-), 14 (5.7%) ki-67(+) and 29 (11.9%) M30(+). Of 13 (35%) CTC(+) metastatic pts, 6 (46%) had ki-67(+) CTCs (p=0.037) whereas 54 (40%) of total CTCs were ki-67(+) (p<0.001). No M30(+) CTCs were detected. When sequential samples of the 8 DC who relapsed were analyzed, 2 (25%), had only ki-67(-)/M30(-) CTCs, 6 (75%) had ki-67(+) and 4 (50%) M30(+) CTCs. The respective numbers in the non-relapsed group were 4 (50%), 3 (37.5%) and 3 (37.5%). Moreover, ki-67(+) CTCs were more frequently observed in samples of the relapsed pts (29.6% vs 13.1%). Among 382 CTCs detected in all sequential samples from the relapsed group, 337 (88.14%) were ki-67(-)/M30(-), 26 (6.7%) ki-67(+) and 20 (5.1%) M30(+), whereas the respective percentages among 78 CTCs in non-relapsed pts were 77.6%, 6.5% and 15.8% (p=0.001). Conclusions: The great majority of CTCs detected in DC with BC express neither proliferation, nor apoptosis markers. However, the apoptotic index in CTCs is increased during clinical dormancy, whereas the proliferation index is increased on relapse. In addition, apoptotic CTCs are more frequently encountered during follow-up in DC free of relapse. The above observations suggest that monitoring proliferation and apoptosis in CTCs during clinical dormancy could be used to predict subsequent late relapse.