Re-evaluation of HER2 status in metastatic breast cancer and tumor-marker guided therapy with vinorelbine and trastuzumab

Background: HER2 is overexpressed in 20 - 30% of breast cancers.
Compared to chemotherapy alone, chemotherapy with trastuzumab
improves clinical outcome in patients with HER2- positive
metastatic breast cancer ( MBC). In general, HER2 status in a
primary lesion predicts the status of metastases, so that biopsy of
metastatic lesions appears unnecessary. Case Report: A 39- year old
woman was diagnosed with primary breast cancer in November 2000.
Using the method and scoring system of the DAKO Hercep Test, the
tumor has shown low HER2 expression ( DAKO score 1+). After failure
of several chemotherapy regimens for metastatic disease ( liver,
skeletal), the patient underwent CT- guided needle biopsy of the
liver which showed HER2 positive adenocarcinoma ( DAKO score 3+).
In consequence, the patient was treated with vinorelbine ( 30 mg/
m(2) d1,8,15 q4w) and trastuzumab ( 4 mg/ kg loading dose, 2 mg/ kg
weekly). During a treatment period of 4 months imaging results as
well as tumor marker kinetics indicated an excellent response with
sustained decrease of tumor markers. A retrospective analysis of
the HER2 shed antigen in metastatic stage revealed excessively
increased serum levels and supports HER2 overexpression observed in
liver metastasis. The kinetics of the HER2 shed antigen during
therapy for metastatic disease were found to be in phase with the
kinetics of CEA and CA15- 3. Conclusion: This case report
demonstrates that re- evaluation of the HER2 status may be helpful
in single patients not sufficiently responding to treatment of
metastatic disease. Determination of HER2 overexpression may be
facilitated by a determination of the HER2 shed antigen level in
peripheral blood.