Serum human epidermal growth factor receptor 2 levels as a real-time marker for tumor burden in breast cancer patients

Background and Objectives Human epidermal growth factor receptor 2 (HER2) status, an important factor in the treatment of breast cancer patients, is usually determined using primary tumor tissue samples; however, the HER2 status of metastatic lesions may differ from that of the primary tumor, but biopsies cannot be performed in all cases. Here, we investigated whether serum HER2 levels can serve as an alternative to assessments of HER2 expression in cancer tissues. Methods Between April 2008 and July 2009, serum HER2 levels were evaluated in 295 patients with newly diagnosed breast cancer, 1,068 patients under follow-up care without recurrence after curative surgery, and 82 patients with disease recurrence. Results Among 303 patients with histologically confirmed HER2-positive tumors, the rates of serum HER2 elevation were 9.2% in preoperative patients, 0.9% in patients under follow-up care without recurrence, and 44.0% in patients with recurrent disease; for patients with HER2-negative primary tumors, the corresponding values were 0.8%, 2.6%, and 15.8%, respectively. Conclusion Our results suggest that serum HER2 could be a useful real-time marker for tumor burden and recurrence in patients with HER2-positive disease. J. Surg. Oncol. 2014 109:421–425. © 2013 Wiley Periodicals, Inc.