Change in HER2 status after neoadjuvant chemotherapy and the prognostic impact in patients with primary breast cancer

We aimed to assess change in HER2 status after neoadjuvant chemotherapy (NAC) in patients with primary breast cancer and the prognostic impact of such changes.

The study comprised 588 patients with a non-pathologic complete response who received anthracycline and/or taxane-based regimens in NAC setting. HER2 status was assessed before NAC and in residual invasive tumor of the surgical specimens. The associations between the change in HER2 status and clinicopathological factors were assessed.

Before NAC, 489 (83%) of the 588 patients had HER2-negative tumors and 99 patients (17%) had HER2-positive tumors. Eleven (2.2%) of the HER2-negative tumors changed to HER2-positive, while 33 (33%) of the HER2-positive tumors changed to HER2-negative. ER and PR-positivity before NAC were associated with loss of HER2-positivity, whereas receiving trastuzumab was not. In terms of disease-free survival, there was no difference between patients with and those without change in HER2 status after NAC in either the patients with HER2-negative tumors (P = 0.26) or with HER2-positive tumors before NAC (P = 0.23).

Our results showed that changes in HER2 status did not affect patients' prognosis. Further studies are needed to determine whether HER2-targeting agents can be omitted when loss of HER2-positivity is confirmed after NAC.