A B S T R A C T PurposeWe evaluated whether patients with human epidermal growth factor receptor 2 (HER2) -positive primary breast tumors had metastatic tumors that were HER2 positive (concordant) or HER2 negative (discordant). We then evaluated whether treatment with trastuzumab or chemotherapy before biopsy of the metastasis had any effect on the rate of HER2 discordance. We also compared the overall survival durations of patients with HER2-concordant and -discordant tumors. Patients and MethodsWe retrospectively identified all patients who initially had been diagnosed with HER2-positive (immunohistochemistry 3ϩ and/or fluorescent in situ hybridization positive) primary breast cancer between 1997 and 2008 at MD Anderson Cancer Center who also had metastatic tumor biopsy results available for review. ResultsWe included 182 patients who met our criteria. Forty-three (24%) of the 182 patients with HER2-positive primary tumors had HER2-negative metastatic tumors. The HER2 discordance rates differed significantly on the basis of whether patients received chemotherapy (P ϭ .022) but not on the basis of whether patients received trastuzumab (P ϭ .296). Patients with discordant HER2 status had shorter overall survival than did patients with concordant HER2 status (hazard ratio [HR], 0.43; P ϭ .003). A survival difference remained among the 67 patients who received trastuzumab (HR, 0.56; P ϭ .083) and 101 patients who did not (HR, 0.53; P ϭ .033) before their metastasis biopsies. ConclusionWe confirmed that loss of HER2-positive status in metastatic tumors can occur in patients with primary HER2-positive breast cancer. Our data strongly support the need for biopsies of metastatic lesions to accurately determine patient prognosis and appropriate use of targeted therapy.

In patients with Dukes' stage B and C CRC who require adjuvant chemotherapy, detection of CEA/CK/CD133 mRNA in PB is a useful tool for determining which patients are at high risk for recurrence and poor prognosis.