P3.05 A New Non-Toxic Hybridization Buffer Reduces the Fish Assay Time From 16-20 Hours to 3½ Hours Without Compromising the Quality

Abstract

ABSTRACT Fluorescence in-situ hybridization (FISH) is a powerful technique for direct visualization and quantitative determination of gene amplifications, deletions and translocations in human cancer cells. It is recognized as a reliable and reproducible method, and FISH assays are often referred to as 'Gold Standard' for determining the patient status with predictive tests for HER2 and ALK. But FISH is also known to have characteristics which limit a more widespread use, including the long assay time (staining and scoring), requirement for a fluorescence microscope and complexity involved in handling small volumes and toxic reagents. Dako has addressed the toxicity and long hybridization time by introducing a new hybridization buffer. The new non-toxic hybridization buffer (IQFISH buffer), which allows for significant reduction in hybridization time, brings the total assay time for a FISH assay down from 16-20 hours to just 3½ hours without compromising the quality. The new Dako HER2 IQFISH pharmDx™ (assay time 3½ hours) has been compared with the traditional Dako HER2 FISH pharmDx™ Kit (assay time 16-20 hours) in a comparative study on 78 breast tissue specimens of human breast carcinoma ( Fig 1 ). Cross tabulation of HER2 status obtained by the two assays gave an overall agreement of 98.7% (95% CI: 94.2%-99.9%). Disagreement between the two assays was observed for one specimen that most likely was a heterogeneous tissue with a very small area of amplification. A similar comparative study on 79 gastric adenocarcinoma specimens showed an overall agreement of 98.7% (95% CI: 94.2%-99.9%). The disconcordant sample was a heterogeneous tissue with a very small area of amplification. A third concordance study on 80 breast cancer tissues compared TOP2A IQFISH pharmDx™ with the traditional TOP2A FISH pharmDx™ Kit ( Fig 2 ). A 100% overall agreement (95% CI: 96.9%-100%) was found. Conclusion: We have developed new non-toxic hybridization buffer that by reduction of the hybridization time from 16 to 2 hours allows for a ½ day FISH protocol. The IQFISH buffer has been validated for HER2 on breast and gastric cancer and for TOP2A on breast cancer. Both assays showed a very high agreement with the traditional 2 day FISH procedure. Download : Download full-size image Fig. 1 . Agreement between the new Dako HER2 IQFISH pharmDx™ and the traditional Dako HER2 FISH pharmDx™ Kit. Download : Download full-size image Fig. 2 . Agreement between the new Dako TOP2A IQFISH pharmDx™ and the traditional Dako TOP2A FISH pharmDx™ Kit.