Circulating tumor cells during and beyond maintenance therapy with SERM or aromatase inhibitors for decision making in long-term survivorship.

119 Background: Although current guidelines still support 5 years of hormone blocking therapy after primary breast cancer due to earlier results showing no benefit of longer treatment, recent data have shown that longer treatment with tamoxifen can better reduce recurrence and death. However, side effects with this therapy can be considerable and compliance declines with time. We, here, report data on monitoring circulating epithelial tumor cells (CETC) beyond maintenance therapy showing that even if maintenance therapy with SERM or aromatase inhibitors had been effective in reducing tumor cells in blood, there can be a reincrease after the end of maintenance therapy and that this is highly correlated with relapse. Methods: 7.5ml of anti-coagulated blood was drawn before the start of chemotherapy, after each cycle and after the end of chemotherapy. Using a nondissipative approach with only red blood cell lysis the white blood cells including the tumor cells were stained with a fluorescent labelled anti-ep...