Chen, B

Abstract Background: Prediction of benefit from trastuzumab in patients (pts) with HER2+ breast cancer remains an important goal. We sought to investigate the predictive value of quantitative measurement of HER2, HER3, HER4, EGFR, ER and PTEN protein expression on the benefit of trastuzumab in the phase III HER2+ adjuvant N9831 study for pts randomized to chemotherapy alone (Arm A) or chemotherapy with sequential (Arm B) or concurrent trastuzumab (Arm C). Methods: For each marker, we evaluated quantitative expression, relationship with demographic data, and association with disease-free survival (DFS) of pts. Freshly cut tissue microarray slides with up to three-fold redundancy per specimen from the N9831 cohort were treated identically using the AQUA (Camp, et al; Nat Med 2002, JCO 2008) method of quantitative immunofluorescence for each marker. HER2 was tested with CB11 (mouse monoclonal, Biocare, Inc.) and preliminary results were available for 698 of nearly 1400 pt specimens to be tested. The minimum value per pt was used in statistical analysis. Specimens were classified with high versus low expression based on a median value cutpoint for each marker. Median follow-up was 7.0 yrs. Results: Quantitative HER2 was compared with centrally performed HER2 testing by IHC and FISH. Median quantitative HER2 via AQUA was 10,017 units for the HER2 IHC 3+ group (n=607) versus 1058, 831, and 970 for the HER2 IHC 2+ (n=68), 1+ (n=11), and 0 (n=11) groups, respectively. The Spearman correlation between quantitative HER2 and FISH HER2/CEP17 ratio was 0.32 (p<0.001). High quantitative HER2 was associated with lower percentage of hormone receptor positivity (48% vs 59%, chi-sq p=0.003) but not associated with age, race, nodal positivity, tumor histology, grade, or size. High HER2 did not impact DFS in any arm of the study (See Table). Data for additional HER2 testing, HER3, HER4, EGFR, ER and PTEN are in process and will be ready by September, 2011. Conclusions: Similar to results based on standard HER2 testing by IHC and FISH in N9831, quantitative HER2 did not impact benefit from adjuvant trastuzumab. Results for additional markers will be presented. Our complete quantitative results for a second epitope on HER2, HER3, HER4, ER and EGFR will be the first report of these markers in a large patient cohort in the adjuvant setting. Disease Free Survival Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr PD05-03.

Abstract Identification of HER2 as an important cellular marker in the biology and treatment of breast cancer has highlighted the importance of reliable testing methodology. Controversy exists regarding type of test, reliability, definition of positivity, and which test may best predict for patient (pt) efficacy to anti-HER2 therapies. Purpose: To determine the concordance between HER2 results by 3 central laboratories, impact of round-robin adjudication of discordant cases, and heterogeneity in HER2 results using specimens from 3 adjuvant trials where HER2 testing was performed by local and central laboratories for enrollment. Methods: We performed a blinded round-robin exchange of randomly sampled, HER2-normal (IHC-& FISH-) and HER2-positive breast tumors among 3 central laboratories (NCCTG, BCIRG and NSABP) for confirmatory HER2 testing. The 3 laboratories performed immunohistochemistry (IHC) for HER2 using the HercepTest kit (Dako, Carpenteria, CA) and fluorescence in situ hybridization (FISH) for HER2 using the PathVysion HER2 DNA probe kit/HER2/CEN17 probe mixture (Abbott Molecular, Des Plaines, IL) on 389 tumor specimens obtained from N9831/BCIRG006 (37 IHC+/FISH+, 33 IHC+/FISH-, 36 IHC-/FISH+, 62 IHC-& FISH-) and BCIRG005 (96 IHC-& FISH-); 123 cases had ≥2 blocks examined from the same pt. HER2 positivity was defined according to FDA-approved guidelines used in the clinical trials (IHC+: 3+ complete membrane staining in >10% cells; FISH+: HER2/CEN17 ratio ≥2.0). The HER2 status (IHC: 3+ vs 0-2+; FISH: amplified vs not) for each block was independently determined at each site; discordant IHC and FISH cases were adjudicated at a face-to-face meeting. Results: Independent reads were concordant across pathologists in IHC status in 351/381 (92%) cases and in FISH status in 343/373 (92%) cases. Upon adjudication, a consensus was reached on 16 and 18 of the discordant IHC and FISH cases, respectively. Among 96 BCIRG005 cases, IHC-and FISH-were confirmed in the primary block in all 96 cases. Among 59 evaluable N9831 HER2-normal cases, IHC-and FISH-were confirmed in the primary block in 57 (97%) cases (but another block tested HER2+ for 4 cases). Among 102 N9831/BCIRG006 HER2+ cases, HER2 positivity was confirmed in the primary block in 73 (72%) cases. Among 118 cases with IHC results for > 1 block, the adjudicated IHC result agreed across blocks in 106 (90%) cases. Among 113 cases with FISH results for >1 block, the adjudicated FISH result agreed in 107 (95%) cases. Among 53 N9831 HER2-normal cases adjudicated as IHC-& FISH-(although they all had a previous local HER2+ test), there was significant improvement in disease-free survival associated with trastuzumab given concurrently with paclitaxel after doxorubicin and cyclophosphamide compared to chemotherapy alone (HR=0.31, 95% CI 0.11-0.91; A 23 pts, 10 events; C 30 pts, 5 events). Conclusions: Excellent agreement (96%) was observed among the pathologists at adjudication, suggesting that standardized methods improve assay proficiency. HER2 heterogeneity across blocks was observed more at the protein than at the gene level. In the small subset of N9831 pts adjudicated as HER2-normal trastuzumab benefit was observed. This work was supported by NCI and Genentech. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr PD10-02.

Abstract In the Breast International Group (BIG) and North Central Cancer Treatment Group (NCCTG) co-led phase III adjuvant breast cancer trial, ALTTO (Adjuvant Lapatinib and/or Trastuzumab Treatment Optimisation), two central laboratories, the European Institute of Oncology (IEO; Milan, Italy) and Mayo Clinic (Rochester, MN), are responsible for confirming the human epidermal growth factor receptor-2 (HER2), estrogen receptor α(ER), and progesterone receptor status of the primary breast tumors for the Rest of World (excluding China, which conducts a separate central review) and North American patients, respectively, prior to patient study entry. As of December 2009, discordance in HER2 and ER testing between local and central laboratories was observed by both central laboratories. For IEO, 14.5% of 8,037 HER2 cases locally positive [by either immunohistochemistry (IHC) or fluorescence in situ hybridization (FISH)] were not able to be confirmed as centrally positive; whereas for Mayo, 5.8% of 412 HER2 cases locally positive were not able to be confirmed as centrally positive (Table 1). Central and local IHC ER discordance was 12.1% and 11.7% for 9,021 IEO screened cases and 419 Mayo screened cases, respectively (Table 2). In particular, IEO observed more false-positive (locally positive/centrally negative) HER2 findings than Mayo and Mayo observed more false-positive ER findings than IEO. Purpose: Motivated by the above findings, we launched a ring study to assess whether the central lab results of a subset of local/central discordant ALTTO cases could be confirmed in the other central lab. Methods: IEO and Mayo exchanged and retested a subset of FFPE breast tumors collected in ALTTO. IEO sent 20 HER2 false-positive, 5 ER false-positive, and 5 ER false-negative (locally negative/centrally positive) ALTTO breast tumors to Mayo. Mayo sent 5 HER2 false-positive, 20 ER false-positive, and 5 ER false-negative ALTTO breast tumors to IEO. IEO and Mayo performed IHC for ER according to their own methodology: DAKO cocktail of ER 1D5 and 2.123 monoclonal antibodies and monoclonal ER 1D5 antibody, respectively. The two laboratories performed IHC for HER2 according to the HercepTest® manufacturers’ instructions (Dako, Carpenteria, CA) and FISH for HER2 using the PathVysion HER2 DNA probe kit and the HER2/centromere 17 probe mixture (Abbott Molecular, Des Plaines, IL). Results: IEO and Mayo confirmed the central HER2-negative result in 100% of 25 cases. Analyses of ER are ongoing and ER results will be presented. Conclusions: In this subset of patients, enrollment ineligibility did not change when HER2 testing was performed by either IEO or Mayo Clinic central laboratories. Table 1. HER2 Local/Central Lab Results Table 2. ER Local/Central Lab Results Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-10-36.