Abstract P6-17-38: Clinical and pathological features of breast cancer with 'polysomy' of Chromosome 17
Authors: Sun H , Chen H , Lim B , Sahin AA 
Published: May 2019

Background: Anti-HER2 therapy is a standard of care for patients with HER2+ breast cancer. HER2 status is routinely evaluated using immunohistochemical stain and/or florescence in situ hybridization (FISH). Interpretation of FISH results may be challenging in tumors with 'polysomy' of chromosome 17 ('polysomy'17), which is defined by increased chromosome enumeration probe 17 (CEP17) signal number. There is evident that 'polysomy'17 might account for anti-HER2 therapy response in breast cancer (BC) with normal HER2/CEP17 ratio. This study aims to study the clinical and pathological features of BC with 'polysomy'17. Method: Primary BC were selected based on elevated CEP17 count (≥3.0) in HER2 FISH performed at MD Anderson Cancer Center between April 2014 and March 2018 (n=385). Patient charts were reviewed for detailed clinical and pathological features. These cases were further divided into four groups according to HER2/CEP17 and HER2 copy number, based on ASCO-CAP guidelines: group 1 (HER2+) – HER2/CEP17≥2.0, HER2 copies≥4.0; group 3 (HER2+) – ratio&lt;2.0, HER2 copies≥ 6.0; group 4 (HER2 equivocal) – ratio &lt;2.0, HER2 copies ≥4.0 and &lt;6.0; group 5 (HER2-) – ratio&lt;2.0, HER2 copies&lt;4.0. Chi-square tests were performed to study the difference of these characters. Results: In comparison with groups 1 and 3, BC in groups 4 and 5 are more commonly seen in elder patients (p=0.001). Also, these tumors show higher pathological category (p&lt;0.001) and higher rate of lymph nodes metastasis (p&lt;0.05). The clinical and pathological features are summarized in [Table 1]. Conclusion: Understanding the clinical and pathological features of BC with 'polysomy'17 may help clinically to choose patients who might be benefit from anti-HER2 therapy. Further study is to follow up the therapy response of those who received anti-HER2 treatment in this cohort of patients.

Clinical and pathological characteristics of breast cancer with 'polysomy' of chromosome 17  Total (N=385)Group 1 ( N=131)Group 3 (N=25)Group 4 (N=69)Group 5 (N=160)P valueAge (year)Mean (range)56.8 (25-94)53.9 (25-83)52.8 (26-75)58 (33-92)59.3 (29-94)0.001Race RaceBlack (%)37 (9.6)14 (10.7)4 (16)5 (7.2)14 (8.8)0.873 Hispanic (%)61 (15.8)23 (17.6)3 (12)12 (17.4)23 (14.4)  White (%)251 (65.2)82 (62.6)14 (56)44 (63.8)111 (69.4)  Other (%)36 (9.4)12 (9.1)4 (16)8 (11.6)12 (7.4) GenderFemale (%)383 (99.5)131 (100)25 (100)68 (98.6)159 (99.4)0.478 Male (%)2 (0.5)0 (0)0 (0)1 (1.4)1 (0.6) Histology typeIDC, NOS (%)350 (90.9)121 (92.4)20 (80)66 (95.7)143 (89.4)0.471 ILC (%)9 (2.3)3 (2.3)1 (4)0 (0)5 (3.1)  Others (%)26 (6.8)7 (5.3)4 (16)3 (4.3)12 (7.5) Nuclear gradeI (%)4 (1.2)2 (1.8)0 (0)1 (1.8)1 (0.7)0.044 II (%)122 (37)30 (26.3)12 (50)19 (33.3)61 (45.5)  III (%)203 (61.8)82 (71.9)12 (50)37 (64.9)72 (53.8)  NA561711226 Pathological tumor categorypT0+Tis (%)61 (21)36 (36.3)3 (20)5 (10.9)17 (13.1)&lt;0.001 pT1 (%)125 (43.2)39 (39.4)7 (46.7)20 (43.5)59 (45.4)  pT2+T3+T4 (%)104 (35.8)24 (24.3)5 (33.3)21 (45.6)54 (41.5)  NA9532102330 Pathological lymph node categorypN0 (%)187 (65.4)81 (82.7)11 (73.3)22 (47.8)73 (57.5)0.048 pN1+N2+N3 (%)99 (34.6)17 (17.3)4 (26.7)24 (52.2)54 (42.5)  pNx (%)9933102333 

Citation Format: Sun H, Chen H, Lim B, Sahin AA. Clinical and pathological features of breast cancer with 'polysomy' of Chromosome 17 [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-38.