Summaries of Must-Read Clinical Literature, Guidelines, and FDA Actions
How New Guidelines Impact FISH Results
J Clin Oncol; 2016 Oct 10; Shah, Wiktor, et al
Adhering to updated immunohistochemistry (IHC) and fluorescent in situ hybridization (FISH) HER2 testing guidelines from ASCO/CAP led to more FISH-equivocal patients in an analysis of nearly 2,000 samples.
Investigators looked at the new guideline’s impact on HER2 FISH amplification frequency. 85% of the samples were IHC 2+. Among these, HER2 FISH positivity was 12% per FDA guidelines, 9% per older guidelines from ASCO/CAP, and 24% per the new ASCO/CAP recommendations. Overall positivity was seen in:
- 12% of those with a FISH ratio ≥ 2.0
- 1% with a FISH ratio ≥ 2.0 despite a HER2 signal < 4.0.
- 3% with HER2 signal ≥ 6.0 despite FISH ratio < 2.0.
Final HER2 positivity was 24% with the new guidelines, 13% with FDA suggestions, and 11% with the older guidelines.
Shah M, Wiktor A, Meyer R, et al. Change in pattern of HER2 fluorescent in situ hybridization (FISH) results in breast cancers submitted for FISH testing: Experience of a reference laboratory using US Food and Drug Administration criteria and American Society of Clinical Oncology and College of American Pathologists Guidelines. J Clin Oncol. 2016;34(29):3502-3510. doi:10.1200/JCO.2015.61.8983.