Triple negative breast cancer -cytogenetic change assessment of EGFR (HERi) and TOP2A genes with clinical and histopathological data analysis

Introduction: Triple negative breast cancer (TNBC) - negative for hormonal receptors (HR) and HER2 receptor (HER2/neu, c-erbB2) - is a subgroup of 10-17 % of all breast cancer cases. Treatment approaches targeted at HR and HER2 are not eligible for these patients because of receptor negativity. The treatment in these cases remains surgery, radiation and chemotherapy. The results however could be improved with the support of biological treatment. Our study focuses on cytogenetic markers for TNBC which could be used as targets for treatment.

Materials and methods: A total of 59 patients diagnosed with nonmetastatic TNBC between 1998-2005 were studied. Histologically their tumors were invasive ductal carcinoma (IDC), invasive lobular carcinoma (ILC), medulary carcinoma (MC) and ductal carcinoma in situ (DCIS). Formalin-fixed paraffin-embedded peroperative tissue samples were prepared for fluorescent in situ hybridization. We evaluated genes encoding for epithelial growth factor receptor (HER1, EGFR) and topoisomerase 2a (TOP2A) in relation to chromosomes 7 and 17 (CH7, CH17), respectively. Amplification (A) cutoff used was EGFR/CH7>1.5, polysomy (P) cutoff used was CH7>2.5. The data were analyzed using standard statistical methods.

Results: Median age was 57 years at diagnosis. We found EGFR amplification in 20.7 % (12/58) cases, high (EGFR/CH7>2.5) amplification was found in 3 patients (25 %). CH7 polysomy occurred in 22.4 % (13/58) cases. Cytogenetic changes involving EGFR amplification and CH7 polysomy were found in 43.1 % (25/58) patients. One case (1.7 %; 1/58) displayed rare EGFR deletion together with TOP2A amplification. Only tumors with nonamplified EGFR carried TOP2A amplifications. These were present in 6 patients (12.8 %; 6/47), high TOP2A amplification (TOP2A/CH17 > 2.5) in 1 patient (16.7 %). TOP2A deletion was identified in 3.4 % (2/59) of all cases. TOP2A/CH17 ratio showed a trend toward asociation with higher HER2 gene copy number (p=0.0883). There was a significant correlation between EGFR amplification and higher grade (G) and negative axillary lymph nodes (p=0.0179, resp. p=0.0086). EGFR polysomic patients tended to be older (p=0.0741). There was a significant relation between MC and young age at diagnosis (p= 0.0069). Lower expression of bcl-2 correlated with higher EGFR gene copy number (p= 0.0194).

Conclusion: Higher G was found in EGFR amplified tissues. In contrast, relation to axillary node involvement revealed an association between N0 and EGFR amplification. Increased EGFR gene copies might therefore enhance tumor proliferation without supporting metastasis. Survival analyses showed no significant differences in patient subgroups. To confirm the outcome in the CMF-treated group and to assess more precisely the impact of radiation we need to increase the patient sample. TOP2A amplifications were found in low frequency in EGFR nonamplified cases. TOP2A is a marker predicting probability of better outcome after anthracycline based treatment. Based on EGFR evaluation we identified patients who might be expected to benefit from EGFR targeted therapy.

The study was supported by MSM6198959216 a LC07017 grants.