Abstract 230P
Background
Complete pathologic response (pCR) in HER2 positive breast cancer patients after neoadjuvant treatment (NAC) is well correlated with high HER2 expression and is a surrogate for survival, but oestrogen receptor positive (ER +) patients have a lower pCR. Therefore, it should be specified which subgroup of these patients could have a higher pCR and would benefit more from NAC.
Methods
We analysed the clinical pathological variables associated with a pCR in a series of 108 patients with early or locally advanced breast cancer with ER + positive tumours and HER2 overexpression who received NAC.
Results
Median age was 54 years (31-89), median tumour size was 39 mm (14-100) and 52 (48%) patients had nodal involvement. Median Ki67 expression was 40% (3-80), 50 patients (57%) showed HER2 overexpression with FISH amplification (HER+ +2). 32 patients (29%) received anti-HER2 therapy with trastuzumab plus pertuzumab and 74 (68%) received anthracycline treatment. A total of 32/108 patients (29,6%) achieved a pCR. In the univariable analysis, oestrogen receptor expression (P: 0,006) and Ki67 level (P:0,015) and HER2 +3 (P:0,004), were correlated to pCR. We found no correlation with other variables or with previous treatment with anthracyclines or pertuzumab plus trastuzumab. In the multivariable analysis, the variables with significance were HER2 +3 expression (OR: 4,49 IC 95% 1,66-12.12) and Ki67 levels higher than 38 (OR: 3,54 IC 95% 1,34.9,35). We summarized the rate of pCR according to these variables with significance, the group with ER+<250 plus Ki67> 38 and HER2 +3 was the most sensitive, with 65% of patients achieving pCR, while the group with RE >250 plus Ki67>38 and HER2 +2 was the least sensitive, with only 6% achieving pCR.
Conclusions
In breast cancer patients with HER2 positive and ER positive tumours, only 29% achieve pCR . Of this group, 60% had a high proportion of equivocal HER2 overexpression and only 14% of the patients in this subgroup achieved pCR . Similarly, 60% of the patients in this group had a KI67 index of less than 38 and only 16% of this subgroup achieved pCR. Oestrogen receptor EXPRESSION, Ki67 index and HER2 expression could help us select the patients with the best chance of obtaining a complete response, especially when they have low expression of ER, High Ki67 index and HER2 +3 expression.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Hospital Arnau De Vilanova De Lleida.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.