Prospective Study of HER2 Status in 1386 Invasive Breast Carcinomas. The Impact of the ASCO/CAP 2007 Guidelines.
Montse Verdu, Marta Gonzalez, Ruth Roman, Natalia Rodon, Carme Pubill, Begonya Martinez, Miriam Gorriz, Beatriz Garcia-Pelaez, Miquel Calvo, Xavier Puig. BIOPAT, Biopatologia Molecular, SL, Grup Assistencia, Barcelona, Spain; Hospital de Barcelona, SCIAS, Grup Assistencia, Spain; Histopat Laboratoris, Barcelona, Spain; Universitat Barcelona, Spain
Background: The introduction of the ASCO/CAP guidelines in 2007 followed the need to unify methodologies used in the HER2 evaluation and to guarantee the predictive test value in the different laboratories. The aim of this study is to review our experience in the assessment of the HER2 status and evaluate the impact of the application of the guidelines in our results.
Design: A cohort of 1386 primary invasive breast cancer formalin-fixed, paraffin-embedded samples, from 2000 to 2010, were prospectively analyzed by immunohistochemistry (IHC) performed by ABC immunoperoxidase staining, using a mouse monoclonal antibody (CB11) and fluorescent “in situ” hybridization (FISH) with chromosome 17 centromeric probe. The IHC results were evaluated following the HercepTest scoring and the FISH results following the manufacturer's recommendations till the implantation of the ASCO/CAP guidelines in 2007.
Results: We observed a decrease in the percentage of positive (14,2 vs 6,7%) and negative (62,4 vs 36,5%) cases by IHC. Nevertheless, using FISH as a gold standard there was an evident improvement in the accuracy of this technique (90,9 vs 97,8%) with an increase in its specificity (91,6 vs 97,8%), sensitivity (87,9 vs 97,7%), positive (71,3 vs 89,6%) and negative (97,0 vs 99,6%) predictive values. The number of equivocal cases also increased considerably (17,2 vs 56,1%). The newly defined FISH equivocal category represents a 5,6% of cases and causes a decrease in the number of positive cases (21,4 vs 16%). Both IHC and FISH results were shown to be significantly dependent on the evaluation method by a loglineal model.
Conclusions: In our experience, the recommendations of ASCO/CAP guidelines significantly increase the number of equivocal results; nevertheless improve the exactitude of the IHC method. Their application decreases the number of positive cases by FISH, and therefore, the indications of specific treatment. The dependency found between IHC and FISH results and the evaluation method should always be taken into consideration when assessing the HER2status.
Tuesday, March 1, 2011 9:30 AM
Poster Session III # 44, Tuesday Morning