Immunohistochemistry and fluorescence in situ hybridization assessment of HER2 in clinical trials of adjuvant therapy for breast cancer (NCCTG N9831, BCIRG 006, and BCIRG 005)

Abstract

A comprehensive, blinded, pathology evaluation of HER2 testing in HER2-positive/negative breast cancers was performed among three central laboratories. Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) analyses were performed on 389 tumor blocks from three large adjuvant trials: N9831, BCIRG-006, and BCIRG-005. In 123 cases, multiple blocks were examined. HER2 status was defined according to FDA-approved guidelines and was independently re-assessed at each site. Discordant cases were adjudicated at an on-site, face-to-face meeting. Results across three independent pathologists were concordant by IHC in 351/381 (92 %) and FISH in 343/373 (92 %) blocks. Upon adjudication, consensus was reached on 16/30 and 18/30 of discordant IHC and FISH cases, respectively, resulting in overall concordance rates of 96 and 97 %. Among 155 HER2-negative blocks, HER2 status was confirmed in 153 (99 %). In the subset of 102 HER2-positive patients from N9831/BCIRG-006, primary blocks from discordant cases were selected, especially those with discordant test between local and central laboratories. HER2 status was confirmed in 73 (72 %) of these cases. Among 118 and 113 cases with IHC and FISH results and >1 block evaluable, block-to-block variability/heterogeneity in HER2 results was seen in 10 and 5 %, respectively. IHC−/FISH− was confirmed for 57/59 (97 %) primary blocks from N9831 (locally positive, but centrally negative); however, 5/22 (23 %) secondary blocks showed HER2 positivity. Among 53 N9831 patients with HER2-normal disease adjudicated as IHC−/FISH—(although locally positive), there was a non-statistically significant improvement in disease-free survival with concurrent trastuzumab compared to chemotherapy alone (adjusted hazard ratio 0.34; 95 % CI, 0.11–1.05; p = 0.06). There were similar agreements for IHC and FISH among pathologists (92 % each). Agreement was improved at adjudication (96 %). HER2 tumor heterogeneity appears to partially explain discordant results in cases initially tested as positive and subsequently called negative.Electronic supplementary materialThe online version of this article (doi:10.1007/s10549-013-2444-y) contains supplementary material, which is available to authorized users.

OPTIMA prelim: a randomised feasibility study of personalised care in the treatment of women with early breast cancer

“…Such patients would ordinarily be treated with adjuvant trastuzumab but received this treatment only by virtue of agreeing to join the OPTIMA prelim. The evidence of benefit for adjuvant trastuzumab treatment for cases with equivocal HER2 amplification 195 is controversial.…”

Quantitative Assessment of Immunohistochemistry Laboratory Performance by Measuring Analytic Response Curves and Limits of Detection

“…Also, heterogeneity of cell expression within a single tumor can further confound the analysis. 30,31 In such instances, discrepant test results on serial sections of the immunostains. These data were provided by the same laboratories from which analytic response curves were measured (Figure 7).…”

What do providers, payers and patients need from comparative effectiveness research on diagnostics? The case of HER2 / Neu testing in breast cancer

“…This debate is further challenged by the complexity of factors impacting the studies and interpretation of results on HER2 protocols. For example, tumor heterogeneity has been found to impact the concordance of HER2 testing protocols [37,38]. Recently, HER2 testing and the use of related therapies were also recommended for gastric and esophageal cancer patients [107].…”

“…These factors challenge CER on diagnostic protocols, because comparative technical performance of alternative protocols provides pivotal information for studies on comparative cost, cost-effectiveness or patient outcomes. Evolving knowledge of tumor biology introduces new factors, such as tumor heterogeneity [37,38], that may further complicate the development of evidence and interpretation of results.…”