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Citation: European Journal of Cancer Supplements Volume 8, No.3, March 2010, page 115

H. Makino1, K. Kuninaka1, C. Yoshida1, H. Hashidate2, M. Siotani3

1Niigata City General Hospital, Breast Oncology, Niigata, Japan
2Niigata City General Hospital, Pathology, Niigata, Japan
3Niigata City General Hospital, Radiology, Niigata, Japan

Background: Tumor markers can be an easier modality to detect cancer metastasis compared with diagnostic imaging, and its decrease or increase is often correlated with effectiveness of treatment.
Patients and Methods: Serum human epidermal growth factor receptor 2 extracellular domain (HER2-ECD) levels were reviewed in 56 breast cancer patients with metastasis and 21 patients who underwent preoperative systemic therapy (19: chemotherapy, 2: endocrine therapy). Patients were stratified into 2 groups, those with HER2-positive (group I) and negative (group II) breast cancer.
Results: In patients with metastatic disease, median serum HER2-ECD level was 14.6 ng/ml (group I) vs 12.9 ng/ml (group II, p = 0.14). furthermore, HER2-ECD levels were assessed in 17 patients at the detection of metastasis. In those, HER2-ECD was significantly higher in patients of group I (median: 17.2 ng/ml) than group II (12.2 ng/ml, p = 0.03), and proportion of patients with raised HER2-ECD (>15.3 ng/ml) was 75% (group I) vs 23% (group II, P = 0.099). In patients who undergoing preoperative treatment, median HER2-ECD level was 12.8 ng/ml (group I) vs 9.5 ng/ml (group II, p = 0.28). Proportion of patients with raised HER2-ECD was significantly higher in group I (60%) than in group II (0%, p = 0.008). In those patients, HER2-ECD levels decreased following chemotherapy, and were observed to be less than 15.3 ng/ml in patients who achieved pathological complete response. In 11 patients (85.7%) out of 14 who were evaluated both HER2-ECD levels and imaging diagnosis following systemic therapy, HER2-ECD was successfully associated with tumor response.
Conclusion: Serum HER2-ECD levels were observed to be raised in 75% of HER2-positive breast cancer patients at the time of detection of metastases, and well associated with tumor response in 85.7% of patients.