Qualifying Patients for Herceptin Therapy

The study showed that the pathologist with the lowest manual accuracy (42%) equaled the accuracy of the most accurate manual reader (91%) when using the system, called the Automated Cellular Imaging System (ACIS).

The purpose of the study was to compare ACIS-assisted immunohistochemical (IHC) evaluation of HER2 protein expression to manual IHC and evaluation by fluorescence in situ hybridization (FISH), which measures copies of the HER2/neu gene rather than its protein. Data from the study show a high correlation (92%) between ACIS and FISH scores.

More than 1,250 staining intensity scores of breast cancer patient samples were evaluated by 10 pathologists. The concordance among manual IHC scores and FISH scores reflected the experience levels of the individual reviewers, ranging from 42-92%. When the pathologists repeated their evaluation using ACIS, the concordance increased to a range of 88-96%. Scoring reproducibility also increased, from 72% to 95%, when ACIS was used

ACIS is the product of ChromaVision Medical Systems, Inc. (San Juan Capistrano, CA, USA). The company states that the study data address a widespread public health concern that current manual testing methods for qualifying patients for Herceptin are potentially inaccurate and subjective.

Although FISH is a reliable method for assessing the number of copies of the HER2/neu gene, it has not been approved for guidance of Herceptin therapy and is not currently performed in most laboratories. The only method approved for guiding Herceptin therapy is the HercepTest kit from Dako (Carpinteria, CA, USA), which was used in the study. According to ChromaVision, an estimated 90% of laboratories currently use IHC with manual microscopy for evaluation of HER2 expression.