[181] Reliability of Chromogenic In Situ Hybridization (CISH) for Detecting HER2 Gene Status in Breast Cancer: A Study of Two Institutions Using Manufacturers' Scoring Criteria and the New ASCO/CAP Recommendations

Y Gong, W Sweet, YJ Duh, L Greenfield, J Zhao, E Tarco, WF Symmans, J Isola, N Sneige. University of Texas M. D. Anderson Cancer Center, Houston, TX; Invitrogen Corporation, Camarillo, CA; StatServ Consulting, Inc., Chino Hills, CA; Institute of Medical Technology, University of Tampere, Tampere, France, Metropolitan

Background: The new ASCO/CAP guidelines mandated that a new HER2 assay should show 95% concordance with another validated test for positive and negative results before routine application. Chromogenic in situ hybridization (CISH) has recently showed a potential to replace fluorescence in situ hybridization (FISH) to determine the HER2 gene status, owing to being relatively straightforward and simpler on interpretation. However, the reliability of CISH method using the new ASCO/CAP scoring criteria has rarely been addressed.
Design: Paraffin tissues of 226 consecutive cases of surgically resected invasive breast carcinomas were retrospectively obtained from two institutions: 110 from M. D. Anderson Cancer Center (site A) and 116 from University of Tampere (site B). We tested CISH and corresponding FISH on the same set of 226 tumors simultaneously at both sites. The results of each test were interpreted by pathologists at each site. Both the new ASCO/CAP guidelines and manufacturers' scoring criteria were used to interpret CISH and FISH results.
Results: Using the manufacturers' scoring criteria, the concordance between CISH and FISH was 98.5% at site A and 98.6% at site B, and the reproducibility of CISH results between the two sites was 99.0%. When a three-category criterion (amplified, equivocal and non-amplified) defined by ASCO/CAP guidelines was used, the concordance between the two methods was 95.0% at site A and 96.4% at site B, and the reproducibility of CISH results between sites was 98.5%. When the two-category criterion (ie, excluding equivocal cases) was used for comparison, the concordance between the two methods was 99.0% at site A and 99.1% at site B, and the intersite agreement on CISH results was 100%.
Conclusions: High correlation was oberved between CISH and FISH at the two sites, using manufacturers' and the ASCO/CAP scoring criteria. The concordance exceeds the minimum concordance rate (95%) mandated by the ASCO/CAP for positive and negative results. This study also showed excellent reproducibility of CISH results between test sites.
Category: Breast

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 46, Tuesday Morning