The original HER2 by fluorescent in situ hybridization (FISH) status categorizations from the BCIRG trials were confirmed in an analysis involving nearly 10,500 individuals.

Investigators reevaluated HER2 FISH status in BCIRG-005/006/007 participants per current ASCO-CAP guidelines. They looked at correlations with HER2 protein, clinical outcomes by disease-free and overall survival, and benefit from trastuzumab therapy. Among the results:

• 41% were in ASCO-CAP ISH group 1, 0.7% in group 2; 0.5% in group 3, 4% in group 4, and 54% in group 5.

• Distributions were similar in screened and accrued subpopulations.

• Among accrued patients, FISH group 1 breast cancers were strongly correlated with immunohistochemistry 3+ status; other groups were not.

• Groups 2, 4 and, 5 were strongly correlated with immunohistochemistry 0/1+ status; group 3 was not.

• In BCIRG-005 patients, group 4 was not linked with significantly worse disease-free or overall survival vs group 5.

• In BCIRG-006 patients, only group 1 showed a substantial benefit from trastuzumab.

Citation: Press M, Sauter G, Buyse M, et al. HER2 gene amplification testing by fluorescent in situ hybridization (FISH): Comparison of the ASCO-College of American Pathologists guidelines with FISH scores used for enrollment in Breast Cancer International Research Group Clinical Trials. [Published online ahead of print August 29, 2016]. J Clin Oncol. doi:10.1200/JCO.2016.66.6693.