Abstract P4-09-09: Characteristics of stage 1 to 3 breast cancer patients with amplification of centromere of chromosome 17

Ioannis Voutsadakis; Vanessa Davies

doi:10.1158/1538-7445.SABCS19-P4-09-09

Background: Amplification of the centromeric region of chromosome 17 (CEP17) as measured by In Situ Hybridization (ISH) of the CEP17 probe is used clinically as part of the ISH assay for HER2 status determination in breast cancer. The value of amplification of CEP17 beyond its use in the HER2 ISH test and characteristics of cases bearing CEP17 amplification, have not been fully explored. Methods: A retrospective review of charts of patients with stage 1 to 3 breast cancer that had a dual probe HER2/ CEP17 FISH test in our cancer center during an eight-year period was performed. Data on demographic, and cancer-specific characteristics of the included patients were extracted. The group of patients with an amplified CEP17 defined as mean copy number ≥3 per nucleus was compared with the group without amplification. Results: Two hundred and two patients were included in the analysis. Amplification of CEP17 was observed in 36 patients (17.8%). All patients in the amplified group had a concomitant amplification of HER2 (mean copy number ≥3 per nucleus). In the CEP17 non-amplified group 78 of 166 patients (47%) had an amplified HER2 status. More patients in the amplified group had a clinical HER2+ status according to the 3-protein classifier (33.3% versus 11.5% in the non-amplified group) and less patients in the amplified group had a clinical ER+/ HER2- status (63.9% versus 81.8% in the non-amplified group, x2 p=0.0003). Other significant differences between the amplified and CEP17 non-amplified groups were observed in their lymph node (LN) status (55.6% of patients in the amplified group versus 36.8% in the non-amplified group were lymph node positive, p= 0.04) and in the nuclear heterogeneity component of grade (90.9% of patients in the amplified group were nuclear grade 3 versus 66.9% in the non-amplified group, p= 0.02). There were no statistically significant differences between the groups in overall stage, grade, menopause status or histology. Conclusion: Patients with amplification of CEP17 had a co-amplified HER2 and were more commonly HER2+, LN positive and grade 3 in the nuclear component of grade. Citation Format: Ioannis Voutsadakis, Vanessa Davies. Characteristics of stage 1 to 3 breast cancer patients with amplification of centromere of chromosome 17 [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-09-09.

Abstract P4-09-09: Characteristics of stage 1 to 3 breast cancer patients with amplification of centromere of chromosome 17

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