WHEN IT COMES TO HER2NEU TESTING, a study of accuracy just published by the journal Cancer may raise interesting questions for pathology groups across the nation.
“Assessing the discordance rate between local and central HER2 testing in women with locally determined HER2- negative breast cancer,” was the title of the study published by Cancer on June 13, 2014. (Kaufman et al., Cancer, doi: 10.1002/cncr.28710.)
To determine what discordance might exist between local labs and central labs, the researchers obtained and retested tumor specimens from 530 women. Their goal was to determine if the initial HER2 negative classification had been correct.
Each specimen was retested using both the immunohistochemistry (IHC) and the florescence in situ hybridization (FISH) assays. Each test has FDA clearance.
Researchers determined that the tumor type classification was incorrect for 22 out of the 530 patients. That represented 4% of the patients. Researchers noted that this 4% of patients did not get potentially-efficacious therapy because their HER2 positivity was not determined as a result of those first tests.
Local Pathology Lab Testing
One notable finding was that 18 of the 22 specimens that were categorized incorrectly had been processed at a local laboratory using only one testing method. That caused researchers to hypothesize that the staff at smaller pathology laboratories may be more inclined to use one of the two approved testing methods rather than both. Other limitations of the study were identified.
Lead researcher Peter A. Kaufman, M.D., of Dartmouth-Hitchcock Medical Center, stated: “We, and other groups, have previously shown that a certain percentage of cases found to be HER2 positive in local laboratories are in fact HER2 negative when tested in more experienced central labs.
Accuracy of Negative HER2
“There has, however, been almost no research evaluating the accuracy of a negative HER2 result,” he continued. “This is the first large study to look at this. What is comforting is that we found that re-testing in experienced larger labs confirmed the original local lab results in the majority of cases.”
In their conclusion, the authors wrote: “This study highlights the limitations of employing just one HER2 testing methodology in current clinical practice. It identifies a cohort of patients who did not receive potentially efficacious therapy because their tumor HER2-positivity was not determined by the test initially used. Because of inherent limitations in testing methodologies, it is inadvisable to rely on a single test to rule out potential benefit from HER2-targeted therapy.”
This study is an example of how improving technology, better use of lab test data, and more rigorous QA/QC methodologies are raising the bar on the quality and accuracy of clinical lab and pathology lab testing. It is a reminder to all lab administrators and pathologists that yesterday’s standards of quality, accu- racy, and reproducibility may not meet today’s expectations of physicians, payers, and patients.