Br J Cancer: Retrospective observational study of neoadjuvant therapy for breast cancer

About 15-20% of newly diagnosed invasive breast cancer (BC) patients show overexpression of the HER2 (human epidermal growth factor receptor 2) protein, which is generally due to the amplification of the HER2 gene.
Previous studies have shown that overexpression of HER2 is associated with a poorer prognosis in patients.

According to the ASCO /CAP guidelines for HER2 detection in BC patients , the possible combinations of HER2/CEP17 ratio and HER2 gene copy number were classified into 5 groups.
In 2018, ASCO/CAP released an update showing that group 2 tumors with immunohistochemistry score 2+, HER2/CEP17 ratio ≥2.
0, and HER2 copy number <4.
0 were reclassified as HER2-negative.
This study aims to detect the response of the second group of tumors to neoadjuvant chemotherapy (NACT).

The researchers assessed the association between the HER2 group and pathological complete remission (pCR) by analyzing 749 BC cases identified from 11 institutions.

Summary of breast cancer cohort information

The results showed that 54% of immunohistochemical HER2-positive (score 3+) BC patients achieved pCR, while only 19% of immunohistochemical 2+FISH amplified cases.
27% of the second group of patients treated with HER2 targeted therapy achieved pCR, compared to the combined 1+3 group and 4+5 group with pCR rates of 19% and 11%, respectively.
In the second group and the first group or the combined group 1+3, there was no difference in the pCR rate of patients, but the response rate of the second group was higher than that of the 4+5 group.

In conclusion, when stratified according to the copy number of HER2 gene, no difference in pCR of patients was detected in tumors with a HER2/CEP17 ratio ≥ 2.