SAN ANTONIOBy using a system combining color-based
imaging and automated microscopy, pathologists were able to significantly
improve their accuracy in evaluating HER-2 protein expression in breast cancer
tissue, said Kenneth Bloom, MD, of Rush-Presbyterian-St. Luke’s Medical
In a study presented at the 23rd Annual San Antonio Breast
Cancer Symposium, 10 pathologists evaluated slides from 129 patients with
invasive breast cancer for HER-2 expression using manual immunohistochemistry
(IHC) and fluorescence in situ hybridization (FISH). The IHC analysis was then
repeated using ChromaVision Medical System’s automated cellular imaging
system (ACIS). More than 1,250 staining intensity scores were evaluated.
The pathologists’ previous experience in evaluating HER-2
status ranged from 2 to 3 analyses a week to more than 50 analyses a day. This
range of experience was reflected in their accuracy in manual IHC scoring,
which ranged from 42% to 92%, based on concordance with FISH (Figure 1).
Scoring accuracy improved to a range of 91% to 95% using ACIS-assisted IHC, Dr.
With use of ACIS, the pathologist who was the least accurate
manually (42%) improved to an accuracy equal to that of the most accurate
manual reader (92%) (see Figure 1). "Everybody becomes as good as the
expert with ACIS," he said.
Using ACIS benefits the pathologist by establishing consistency
and uniformity. "The ACIS system can virtually eliminate interlaboratory
variability and allow for consistent and reliable interpretation of IHC results
among pathologists and laboratories," Dr. Bloom said. Agreement among the
10 pathologists was 72% using manual IHC, which improved to 95% with
ACIS-assisted IHC. "Any pathologist evaluating the same slide will get the
same result," he said.
With an IHC-based test, like HercepTest (DAKO, Carpinteria,
California), which was used in the study, the pathologist must analyze the
amount and intensity of the color stain. However, the human eye is limited in
its ability to distinguish various hues of the same color. ACIS, by comparison,
is designed to identify minute differences between cells. It can distinguish up
to 256 levels of intensity of a single color, compared to 4 levels discernible
by the human eye, according to ChromaVision (Figure 2).
The ACIS system scans an area of a slide selected by the
pathologist and shows that area at high power on a monitor. The system uses
color criteria and pattern recognition software to identify the cells that
overexpress HER-2, and then it reports the score to the pathologist.
Breast cancer patients whose tumors overexpress HER-2 are
candidates for trastuzumab (Herceptin), a monoclonal antibody that binds to
HER-2 receptors and slows tumor growth.
The HercepTest is scored manually from 0 to 3+ (0 to
negative; 2+, weak positive; and 3+ strong positive). The cut-off point for
determining trastuzumab treatment in the United States is 2+. Thus, accurate
readings of slides for HER-2 expression are important because they affect the
course of therapy for the patient, Dr. Bloom said.
While FISH also produces a quantitative measurement, it
measures copies of the HER-2/neu gene rather than the expression of
protein. It is also more costly and complex to use than ACIS, according to
The ACIS software can detect one abnormal cell among more than
100 million normal cells, ChromaVision said. The technology had its origins in
the US military’s Star Wars missile defense program, where it was used to
distinguish between active nuclear warheads and decoys. When the military spun
off the technology, ChromaVision (San Juan Capistrano, Calif) acquired the
ACIS, approved by the FDA in 1999, has been available for HER-2
testing for about 1 year. The technology is also being used to measure estrogen
and progesterone receptors, Ki-67, and p53, and to evaluate cancer
micrometastases in bone marrow, lymph nodes, and other tissue.
ChromaVision supplies the technology to labs on a fee-per-use
basis. Clients receive the entire computerized microscopy system, but
ChromaVision retains ownership of the system itself.