Harris, LN

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 Previous findings suggested that patients (pts) with copy number alterations of MYC (8q24) and centromere 8 (CEN 8) in the setting of HER2-positive breast cancer may be associated with improved outcome to adjuvant trastuzumab. Our tissue microarray (TMA) data suggested that alternate cutpoints for MYC copy number anomalies [of 802 pts, those with MYC:CEN8 ratio ≥1.3 or <1.3 & polysomy 8 (N=658; 82%) had a hazard ratio (HR) of 0.44 (P<0.001) and those with MYC copy number ≥2.5 (N=669; 84%) had a HR of 0.42 (P<0.001)] were potentially predictive of benefit from adjuvant trastuzumab when administered concurrently with chemotherapy in the NCCTG N9831 HER2+ phase III trial. Purpose: We were interested in determining whether MYC is the target protein responsible for the suggested benefit from trastuzumab. We evaluated the association between MYC protein expression and disease-free survival (DFS) of pts randomized to receive chemotherapy alone (Arm A) or chemotherapy with sequential (Arm B) or concurrent trastuzumab (Arm C) using N9831 TMAs. Patients/Methods: This analysis included 1220 pts from Arms A, B, and C. The percentage of strong (3+) nuclear staining was determined in TMA sections containing 3 cores per block using immunohistochemistry (IHC; clone 9E10, Sigma-Aldrich, St. Louis, MO). A patient's tumor was considered positive (MYC+) if the maximum nuclear 3+ staining percentage across cores was >30% a priori. Median follow-up was 5.8 years. Results: Of 1220 pts with completed IHC analyses, 557 (46%) were MYC+. MYC+ was associated with a higher rate of hormone receptor positivity (58% vs 48%, chi-sq P<0.001) and higher rate of nodal positivity (92% vs 84%, chi-sq P<0.001) but not associated with age, race, tumor histology, tumor grade, or tumor size. In comparing DFS between arms C and A, MYC+ and MYC-pts had HRs of 0.46 (p=0.002; A: 187 pts, 57 events, C: 161 pts, 25 events) and 0.70 (p=0.09; A: 213 pts, 59 events, C: 208 pts, 38 events), respectively (interaction p=0.20). In comparing DFS between arms B and A, MYC+ and MYC-pts had HRs of 0.74 (p=0.11; B: 209 pts, 52 events) and 0.81 (p=0.29; B: 242 pts, 53 events), respectively (interaction p=0.80) (Figure). In addition, pts with nuclear MYC staining of 3+ in 0-9%, 10-30%, 31-60%, and 61-100% of cells had HRs (C vs A) of 0.98 (95% CI 0.53-1.82), 0.54 (95% CI 0.30-0.97), 0.55 (95% CI 0.27-1.12), and 0.37 (95% CI 0.19-0.75). Conclusions: In our analysis of 1220 pts, we observed that MYC protein expression positively correlated with hormone receptor positivity and nodal status. We observed a trend towards greater trastuzumab benefit among MYC+ as compared to MYC-pts. A rising trend in trastuzumab benefit was observed with increasing MYC protein expression. Analyses including pts with whole sections and outcome by MYC protein and gene copy number will be presented. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P2-09-08.