Her 2 Nu is a gene that is abnormally over expressed in about 20 percent of breast cancers. Because Her 2 Nu is an oncogene that accelerates breast cancer cell division and proliferation when over expressed, it confers an aggressive clinical course and a generally poor prognosis. Fortunately, a monoclonal antibody, Herceptin, has been successfully tested and made available for the treatment of metastatic breast cancer patients whose cancers test positive for Her 2 Nu over expression.
This is usually tested on the tumor tissue at the initial surgery. When some of these patients relapse, Herceptin is used along with other chemotherapeutic agents because of its proven efficacy and safety.
For patients who tested negative for Her 2 Nu over expression at initial surgery, Herceptin would not be considered a treatment option because Herceptin works exclusively on those cancers that over express Her 2 Nu.
At the time of relapse, Her 2 Nu status is not retested because biopsies are not routinely performed if the clinical picture is consistent with metastatic disease. Researchers have now discovered that 15 percent to 20 percent of initially Her 2 Nu negative cancers become positive at the time of recurrence. With knowledge that most primary tumors shed Circulating Tumor Cells (CTC) into the blood stream, researchers developed a way of identifying and capturing these cells from the circulating blood of patients whose cancers have relapsed, for the purpose of testing for Her 2 Nu over expression.
They demonstrated a 97 percent concordance between the initial test on the tumor tissue and the subsequent FISH (Fluorescent In Situ Hybridization) testing for Her 2 Nu over expression on the Circulating Tumor Cells at the time of relapse. Subsequent application of this simple blood test identified 15 percent to 20 percent of patients who converted to a positive status despite being negative for Her 2 Nu over expression at initial surgery.
This has great clinical significance because addition of Herceptin to standard chemotherapy yields better remission rates and outcomes.
These findings were confirmed in a small study of 24 patients. Dr. Jonathan Uhr, professor of medicine at the University of Texas Southwestern Medical Center, said that a simple blood test can be made available if these results can be reconfirmed and validated in larger clinical trials.
-- V. Upender Rao, M.D., FACP, practices at the Cancer and Blood Disease Center in Lecanto.
