Abstract 19P
Background
As new therapeutic strategies in breast cancer (BC) emerge, human epidermal growth factor receptor 2 (HER2) low status has recently proved to have clinical value. There is still limited data available on this subgroup particularly in early settings. We aimed to evaluate the characteristics and prognosis of HER2 low status in patients with early BC.
Methods
We conducted a retrospective observational multicentric study using data from the French CANTO cohort (NCT01993498). Our primary objective was to assess invasive breast cancer-free survival (IBCFS) of HER low compared to HER2 0 BC. Secondary objectives were to evaluate invasive disease-free survival (IDFS), relapse-free interval (RFI) and overall survival (OS). Univariate and multivariate Cox regressions were performed.
Results
We included 9,956 patients with 5,802 HER2 0, 2,513 HER2 1+ and 1,241 HER2 2+ non-amplified (NA) patients corresponding to 9,980 tumours in total. Data were analysed at 100 months and the median follow-up duration was 73 months at this time. HER2 2+ NA tumours were significantly more likely to be larger than 20mm (p < 0.001), to be grade 3 (p < 0.001), to have a ki67 ≥ 20% (p < 0.001) and to be treated by chemotherapy (p < 0.001) compared to HER2 0 and HER2 1+ tumours. HER2 0 tumours were significantly less likely to be hormone receptor (HR) positive (p < 0.001), to have received hormonotherapy (p < 0.001) and were significantly more likely to be lobular tumours (p < 0.001), compared to HER2 1+ and 2+ NA. When we performed the analysis, no significant difference in IBCFS was observed between HER2 0, 1+, and 2+ NA (84.9%, 84.7% and 83.9% respectively, p=0,67). In the multivariate Cox model, HER2 1+ seemed to be associated with a worse IBCFS, but the difference was not significant (p = 0,036). There was no significant association between HER2 score and IDFS, RFI or OS.
Conclusions
We found that in early BC, although there was a significant difference in clinical and histological factors at diagnosis with HER2 2+ NA tumours being more aggressive, there was no significant difference in survival outcomes between HER2 negative and low status. Physiopathological studies and longer follow-up are needed.
Legal entity responsible for the study
Centre François Baclesse.
Funding
Centre François Baclesse.
Disclosure
G. Emile: Non-Financial Interests, Invited Speaker: AstraZeneca, Novartis, Gilead, Seagen, Lilly, Pfizer, Daiichi Sankyo. A. Da Silva: Non-Financial Interests, Invited Speaker: Leopharma, Novartis. All other authors have declared no conflicts of interest.