HER2 status of patients with invasive breast cancer in a population at a single UK centre: Correlation with tumor characteristics

Abstract

11094 Background: The human epidermal growth factor receptor 2 (HER2) overexpression, has been correlated with higher histological grade, increased tumour size, positive lymph node status, and negative or lower oestrogen receptor (ER) expression. Our aim was to look at the association between HER2 status, patient age and tumour histopathologic characteristics. Methods: We analysed retrospectively 735 cases of invasive breast cancer treated between the years 2000 and 2004. HER2 was measured by immunohistochemistry (IHC) and all IHC 2+ tumours were also tested by fluorescent in situ hybridisation (FISH). All information was collected from pathology reports in patient case records. Results: A total of 143 (19.5%) tumours were HER2 positive (120 IHC 3+ and 23 IHC 2+/FISH+). Of the 66 tumours that were IHC 2+, 23 (34.8%) were FISH-positive. The age of most patients (75.8%) was over 50 years but there was a higher incidence (28%) of HER2 overexpresion in the 40–49 age group compared to all other age groups, the incidence of HER2 overexpression was still at least 17–18% in all age groups, including patients aged =70 years. Although, a high proportion of patients (62.2%) had tumours less than 2 cm in size, comparison of tumours less than 2 cm with those greater than 2 cm showed no predictive effect of size on HER2 expression. Over half of the patients had lymph node-negative disease (55.2%) and despite some association of HER2 expression with lymph node involvement (odds ratio of 1.23 for comparison of lymph node-positive versus negative), 19% of lymph node-negative tumours overexpressed HER2. Most tumours were high grade (32.8% grade 3, 44.1% grade 2 ) and although the proportion of HER2 overexpression increased with increasing tumour grade, some grade 1 tumours still overexpressed HER2. A higher proportion (28%) of ER-negative tumours was HER2 positive compared to ER-positive tumours (18%); however, co-expression of HER2 and ER occurred in 14% (105/735) of all primary cancers. Conclusions: In conclusion, it is not possible to predict which patients will be HER2 positive. Therefore, it is essential that HER2 status should be determined in all patients with invasive breast cancer to allow a decision on the use of trastuzumab and guide the choice of chemotherapy. No significant financial relationships to disclose.