Prelminary Results of a NEQAS Ring Study Evaluating the Ventana INFORM™ HER2 Dual Colour Single Slide ISH Assay.

Abstract

Abstract Background: Recent innovations in HER2 testing include the development of novel chromogenic in situ hybridisation tests. Most countries use FISH or ISH based testing for HER2 gene amplification in equivocal (IHC 2+) cases. Data on the reproducibility and portability of novel and even established HER2 ISH methods is sparse. We report initial results from the multicentre evaluation of intra and inter-observer/site variation in scoring HER2 results from 30 breast cancers measured in 5 laboratories using the Ventana Dual colour ISH assay.Methods: A commercially available tissue micro-array (TMA; Stretton Scientific UK) containing 2 replicate cores from 30 breast cancers was circulated to 5 UK NEQAS reference laboratories (numbered 1-5). All laboratories performed chromogenic ISH using a 60 core TMA and reported results for all assessable cores. For all cases 20 cells were scored and a further 20 cells scored on a separate occasion to check intra-observer variation. Results were collated centrally and compared with FISH peformed in a single laboratory. Concordance between FISH and CISH is reported on a core by core and case by case analysis. Intra and inter-observer variation between laboratories is also assessed. Finally regression analysis comparing results was performed. Results from a single laboratory are presented here and full results will be available for the meeting.Results: 93% of cores were successfully analysed by the Ventana dual colour ISH assay. 87% of cores were successfully analysed by PathyVision® FISH CISH was concordant with FISH in 96.4% of cores evaluated. In one sample FISH results were 2.05 & 1.93 vs CISH of 2.03 and 2.14. In a second sample FISH results were 1.60 & 1.53 versus CISH results of 2.00 & 1.65. When mean results were calculated (2 cores per case) concordance between FISH and CISH results for this laboratories was 96.7% (1 discordant case – mean FISH – 1.99, mean CISH 2.09). 48 cores were scored twice (20 cells x 2) by a single observer. Mean intra-observer variation (for HER2 ratio) was 1.72% (Range 0.0-7.42%). No difference in scores was observed for the first vs second 20 cells. Scoring 40 cells produced no advantage. For results from a single observer for 2 cores (intra-site variation) from 42 core pairs (each core counted twice) variation was 7.5%.Conclusions: Preliminary evidence from the current study suggest that the Ventana INFORM™ HER2 dual colour single slide ISH assay can be robustly evaluated using conventional scoring approaches (20 cells per case). Concordance with FISH was excellent in the single laboratory reporting results to date. Further evidence will be reported from the other 4 participating laboratories. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 6011.