Dr. won't do Her2 serum test

[Joe]

EBCC: HER2 Levels May Predict Breast Cancer Response


By Charles Bankhead, Staff Writer, MedPage Today
Published: March 25, 2010
Reviewed by Zalman S. Agus, MD; Emeritus Professor
University of Pennsylvania School of Medicine and

Dorothy Caputo, MA, RN, BC-ADM, CDE, Nurse Planner

BARCELONA -- Monitoring HER2 levels during neoadjuvant breast cancer therapy may improve early identification of patients likely to benefit from trastuzumab (Herceptin), a prospective clinical trial suggests.

Elevated baseline levels of HER2 and a decline of at least 20% during treatment significantly increased the likelihood of pathologic complete response. In multivariate analysis, the 20% decline in HER2 levels remain statistically significant.
"Results of this study demonstrate that prechemotherapy serum HER2 levels as well as a decrease in serum levels to be a significant predictor of response to neoadjuvant chemotherapy for breast cancer," Isabell Witzel, MD, of the Medical University of Hamburg-Eppendorf in Hamburg, Germany, reported here at the European Breast Cancer Conference.
"Monitoring serum HER2 levels in the presence of trastuzumab treatment might be a promising adjunct to clinical evaluation during neoadjuvant chemotherapy in HER2-positive patients."
The neoadjuvant setting offers an opportunity to optimize treatment strategies for patients with nonmetastatic breast cancer. In patients with HER2-positive breast cancer, the extracellular domain of HER2 is shed into the serum, creating potential for a biological role of HER2 during treatment with trastuzumab, Witzel said.
To examine the association between serum HER2 levels and pathologic response, investigators used a commercially available assay to measure HER2 levels before and after neoadjuvant therapy in 90 patients with HER2-positive beast tumors and 85 patients with HER2-negative tumors. All patients with HER2-positive tumors received trastuzumab in addition to chemotherapy.
Pathologic complete response was defined as no microscopic evidence of invasive residual tumor cells in all resected specimens of the breast and lymph nodes. Neoadjuvant therapy led to pathologic complete response in 44 (49%) of HER2-positive patients compared with 12 (14%) HER2-negative patients (P<0.001).
Pretreatment median serum HER2 values were 7.7 ng/mL in the HER2-negative patients and 14.9 ng/mL in the HER2-positive group.
Receiver operating characteristic curve analysis identified 10 ng/mL as the optimal cutpoint for discriminating between HER2-positive and negative tumors, resulting in a sensitivity of 72%, specificity of 85%, positive predictive value of 85%, and negative predictive value of 73%.
Comparing baseline HER2 values and pathologic complete response, the investigators found that a baseline value >15 ng/mL was significantly associated with pathologic complete response (P=0.045). An even stronger association emerged from an analysis of the decline in serum HER2 levels in response to treatment (P=0.02).
In multivariate analysis, a decrease of >20% tripled the likelihood of pathologic complete response (OR 3.2, 95% CI 1.13 to 9.55, P=0.029).