Kinetics of HER2/neu ECD in 45 patients treated with trastuzumab (Herceptin) between January 2001 and June 2005 at the Grenoble University Hospital.

UNLABELLED: The aim of this study was to evaluate the utility of HER2/neu ECD concentration as a marker of the efficacity of clinical response to Herceptin. PATIENTS AND METHODS: Iterative measurements of HER2/neu ECD (ELISA c-erbB2/c-neu Rapid Format Elisa kit QIA10 Calbiochem) concentrations in 45 patients treated with Herceptin between January 2001 and June 2005 at the Grenoble University Hospital. RESULTS: Changes in HER2/neu ECD concentrations were observed in 21 patients (47%). The baseline concentration was the concentration of circulating HER2/neu ECD before treatment with Herceptin. In 15 patients, the mean baseline concentration was 52 ng mL(-1) (extreme values 13-170), which normalized no later than at the time of the 3rd administration of Herceptin. Nine patients (60%) were still alive 5 years later (p<0.05). For 6 patients, the mean baseline concentration was 800 ng mL(-1) (extreme values 140-2000) which persisted and even increased during Herceptin therapy; fewer than 25% were alive 30 months later (p<0.05). In the case of the 24 patients whose HER2/neu ECD concentration remained <5 ng mL(-1), survival time was intermediate. CONCLUSION: The study confirmed the utility of HER2/neu ECD in predicting therapeutic response. However, as in the case of other circulating tumor markers, it is only useful when there is a variation in concentration. This marker should now be evaluated in multi-center studies covering a large number of homogeneous subjects.