P3-05-05: Cyclin D1 Gene Amplification Is Rarely Heterogeneous in Breast Cancer.

Abstract

Abstract Background: Amplification of Cyclin D1 (CCND1) occurs in about 10–20% of breast cancers and has been suggested to predict resistance to anti-hormonal therapy. As the diagnostic accuracy of predictive biomarkers can be substantially limited by regional expression differences within tumors, heterogeneity of CCND1 amplification was assessed in this study. To assess heterogeneity, a novel tissue microarray based analysis platform was developed. Material and Methods: To comprehensively asses the three-dimensional molecular composition of breast cancers, a “heterogeneity TMA” was constructed containing 8 different tissue cylinders from as many different cancer containing tumor blocks as possible (at least 4) from 147 primary breast cancers. Additional tissue samples were taken from 1–4 corresponding nodal metastases from 35 of these patients. Dual labeling fluorescence in situ hybridization (FISH) with probes for CCND1 and centromere 11 was applied. Results: The analysis revealed amplification in 29 of 133 (21.8%) patients with interpretable FISH data. CCND1 amplification was more frequently seen in ductal (22 of 87; 25.29%) than in lobular type (5 of 32; 15.63%) (p=0.251). CCND1 amplification was also associated with high tumor grade with amplification rates of 1 of 18 (5.56%) in grade 1, 15 of 72 (20.83%) in grade 2 and 12 of 40 (30%) in grade 3 carcinoma (p=0.075). CCND1 amplification was more frequently seen in ER positive cases (27 of 110; 24.55%) than in ER negative cases (1 of 17; 5.88%) (p=0.052). No association could be found between CCND1 amplification and tumor stage (p=0.445) and CCND1 amplification and PR status (p=0.752). Heterogeneous amplification status was detected in 9 of 29 (31.0%) amplified tumors, i.e. in 6.8% of all informative cases. Heterogeneity was successfully validated on large sections in all 4 heterogeneous cases with high level amplification. In the remaining 5 “heterogeneous cases” discordant results were due to variable interpretation of borderline amplification results with CCND1/centromer 11 ratios between 1.7 and 2.3. There were no discrepancies seen between primary tumors and matched lymph node metastases. Discussion: The high degree of homogeneity seen for CCND1 amplification suggests that this alteration represents an early event in tumor development/progression in a subset of breast cancers. CCND1 status determined in a small biopsy will be highly representative of the entire tumor and will thus be appropriate for predicting treatment outcome. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-05-05.