Late relapse associated with CEP 17 polysomic breast cancer

Abstract

20011 Background: The clinicopathologic features associated with chromosome enumeration probe 17 (CEP 17) polysomy by fluorescence in situ hybridization (FISH) are not well defined. CEP 17 polysomy is frequently encountered in assessing Her-2neu amplification, which has become an important adjuvant therapeutic target. One mechanism to increase Her-2neu gene copy is polysomy. In this analysis the prognostic and predictive factors associated with CEP 17 polysomy are compared to similar factors in Her-2neu gene amplification. Methods: All cases of Her-2neu gene amplification and CEP 17 polysomic breast cancers from 2000 to present were abstracted. The polysomy group was defined as at least 3 gene copies and was further subdivided into two groups; 3–4 copies and ≥ 5 copies. This resulted in 193 cases of invasive breast cancer, which became the study cohort. Polysomic status and her-2neu gene amplification was compared to age, estrogen receptor (ER), progesterone receptor (PR), grade, tumor size, cell type, mitotic rate, nodal status, number of positive nodes and relapse. Descriptive statistics were used for categorical variables. The χ2 test was used to compare each clinicopathologic factor. Results: Both the ER and PR status was significantly different in the 3 groups. For the Her-2neu amplified, the polysomic 3–4, and the polysomic ≥ 5, the ER positive status was 53%, 67% and 81%, respectively (p = .012). Histologic grade, tumor size and nodal status were not significantly different between groups. Lobular pathology was present in 15% of the polysomy ≥ 5 group, 8% of the polysomy 3–4 group and 1.7% of the amplified group and this difference was significant (p = .03). Relapse disease status was significantly more frequent in the polysomy ≥ 5 group (18.5%) compared to the amplified group (2.6%) (p = .007). Within the relapsed group the median time to relapse was 4 years for the amplified patients versus 12 years and 10 years for the polysomic patients. Conclusion: The incidence of CEP 17 polysomy varies in the literature from 10–50% depending on definitions. Our study is unique in that we divided the polysomic group into 3–4 copies which can be complicated by proliferative activity versus ≥ 5 copies. A significant association between relapse and polysomic breast cancer is described in our dataset. No significant financial relationships to disclose.