HER2 expression has a prognostic and predictive impact in early breast cancer (BC). HER2-positive BC (score 3+ or 2+ with in situ hybridization (ISH) amplification) are treated with anti-HER2 therapies. HER2-low BC (score 1+ or 2+ without ISH amplification) are less defined and until now, no specific treatment has been provided for this subgroup. We tried to explore the response of HER2-low early BC to neoadjuvant chemotherapy (NAC) according to the HER2 score (1+ or 2+).
We designed a retrospective study in two French comprehensive cancer centers. All patient with HER2-low BC treated by NAC from January 2014 to December 2020 were included. First we analyzed the pathological complete response (pCR) to NAC with Sataloff or RCB score, according to the HER2 tumors score. Others objectives were to assess disease free survival (DFS) and overall survival (OS) according to HER2 score. Univariate and multivariate analysis were performed.
We included 237 tumors of 229 patients. Of these, 160 (67.5%) tumors were HER2 1+ and 77 were HER2 2+. Hormone receptor (HR) were positive for 152 tumors (64.1%). The median age was 53.9 years. pCR was achieved in 38 tumors (17%) without difference between HER2 1+ and HER2 2+ subgroups (p=0.77). DFS and OS were statistically worse for HER2 1+ patients compared to HER2 2+ patients (Log-rank p=0.037 and p=0.042, respectively). After adjustment on age, HR and menopausal status, HER2 score was still associated with DFS and OS, with better survival for HER2 2+ patients (HR=0.35 [0.15-0.84], HR=0.24 [0.07-0.81] respectively).
In the HER2-low BC, no difference in pCR were observed between HER2 1+ and HER2 2+ but patients with HER2 2+ BC had a better DFS and OS than others. Further investigations are needed to confirm these results.
Centre François Baclesse.
Has not received any funding.
All authors have declared no conflicts of interest.