Trastuzumab Therapy Optimized by Oncoprotein Blood Test

New research presented at the 93rd annual meeting ofthe American Association for Cancer Research (AACR) suggests that monitoringwith the serum HER2/neu oncoprotein test may help oncologists assess the effectof trastuzumab (Herceptin)-based therapy in patients with metastatic breastcancer. These data add to the growing body of evidence supporting the value ofthe serum HER2/neu oncoprotein test in the management of patients withmetastatic breast cancer.

Serum monitoring provides a "real time" picture of a woman’schanging HER2/neu levels, enabling oncologists to evaluate the effectiveness ofa particular therapy. Studies have shown that decreasing HER2/neu values reflectresponse to therapy, while increasing values may indicate progressive disease.

Data from the study supported the value of the serum HER2/neu oncoproteintest in early prediction of response to trastuzumab-based therapy in metastaticbreast cancer patients. Trastuzumab works by targeting cancer cells thatoverexpress the HER2 protein, and slowing or stopping the growth of these cells.

Study Data

The study was designed to examine whether serial monitoring of serum HER2/neulevels in metastatic breast cancer patients can predict or parallel response totherapy. A total of 3,122 serum samples were taken from 75 women at baseline,and again immediately prior to each infusion of trastuzumab. A decline in serumHER2/neu levels over time correlated to response to trastuzumab. Specifically,the ratio of baseline serum levels to the levels monitored throughout the courseof treatment was significantly higher among patients responsive to therapy thanamong those who did not respond (P ≤ .01). This predictive value was apparentafter the first infusion of trastuzumab.

"These data suggest that monitoring with this oncoprotein blood test canhelp physicians treat their metastatic breast cancer patients," said Dr.Wolfgang Johannes Köstler, clinical division of oncology, department ofinternal medicine at University Hospital in Vienna. "In addition to thehealth implications, optimizing treatment may also have a positive impact oncost."

Further Utility

The serum HER2/neu oncoprotein test has also shown a correlation with patientresponse to traditional hormonal and chemotherapies. A recent study published inthe Journal of Clinical Oncology (19:1698-1706, 2001) concluded that metastaticbreast cancer patients with elevated levels of HER2/neu were less likely torespond to hormonal therapy and had a shorter response duration than patientswith lower levels of serum HER2/neu oncoprotein.

Approximately 50% of women with breast cancer develop distant metastaseswithin 5 years of primary detection. It is estimated that 50% to 70% ofmetastatic breast cancer patients have elevated serum levels of the HER2/neuoncoprotein. Reports have confirmed that an elevated serum HER2/neu level isassociated with poor prognosis, shorter overall survival, and aggressivedisease.