HER-2 expression on circulating tumor cells in metastatic breast cancer.

Abstract

Abstract Abstract #5020 Background: HER-2 Overexpression in breast cancer is associated with poor prognosis. The circulating tumor cells (CTCs) in peripheral blood can be identified in patients with breast cancer. They are recognized as a predictor of the effect of systemic therapy, and also as a prognostic marker recently. Cristofanilli et al reported that progression-free Survival (PFS) and overall survival(OS) in metastatic breast cancer patients with <5CTCs per7.5ml are significantly better than those with >5CTCs before initiation of a new line of therapy and at the 1st follow-up visit. However, the detection rate and value of HER-2 Overexpression on CTCs has been not determined well.Materials and Methods:CTCs were obtained prospectively for 22 patients with metastatic breast cancer to start a new line of treatment at single institution. Blood specimens were collected at monthly intervals for a period of up to 12 weeks. CT scans were also performed before start of the treatment and 12 weeks after. HER-2 expression on primary lesions and CTCs were determined by both immunohistochemical methods and fluorescence in situ hybridization (FISH) analysis. Mean age was 54.4 years (range, 32-75 years). 8 patients received first line therapy, one patient received second line therapy, and 13 patients received over third line therapy. Of the 22 primary cancer, 7(31.8%) were HER-2 positive(score,+3 or +2/FISH positive) and 15 (68.2%) were HER-2 negative. CTCs were determined using Cell Search™ System.Results:14(63.6%) patients had clinical benefit (partial response and stable disease) during the course. CTCs were detected in 16 patients (72.7%). OS for patients with <5CTCs were significantly longer than those with 5< at any period. In 15 patients with HER-2 negative primary cancer, 5 patients (33.3%) were with HER-2 positive CTCs. However, in 7 patients with HER-2 positive primary cancer, 6 patients (85.7%) who had been treated with trastuzumab was with HER-2 negative CTCs. But only one patient (14.3%) treated without trastuzumab was with HER-2 positive CTCs. The patient had been treated with trastuzumab and failed in past. And the median OS time for those patients with HER2 Positive CTCs were significantly shorter (130.5 days) than for those patients with HER2 negative CTCs (283.3 days). Surprisingly, 5 (83.3%) of 6 patients with HER-2 positive CTCs were dead within 7 months.Conclusion:The number of CTCs is a prognostic marker for the patients with metastatic breast cancer. Furthermore, HER-2 positive CTCs is much related to poor prognosis. And these results indicated that the possibility of negative conversion of HER2 expression on CTCs for patients with HER-2 positive primary cancer due to trastuzumab. Trastuzumab may be effective for the patients with HER2 negative primary cancer and HER-2 positive CTCs. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 5020.