HER2 Support Group Forums - ER+her2+ breast cancer IS DIFFERENT

those tumors that respond to neoaduvant chemotherapy and/or targeted therapy with a pCR (pathological complete response ie, no tumor can be detected when the surgical specimen is looked at under the microscope)
have an excellent prognosis as long as those tumors were triple legative or her2+er- to start with. Unfortuanately, the same does not hold true for ER+her2+ tumors even if they respond similarly.

They are still finding out why--whether there are subgroups of them and what the best treatment for them might be

Breast Cancer. 2012 Aug 14. [Epub ahead of print]
Neoadjuvant chemotherapy in breast cancer-insights from the German experience.
von Minckwitz G.
Source
German Breast Group, GBG Forschungs GmbH, Martin-Beheim-Str. 12, 63263, Neu-Isenburg, Germany, Gunter.vonMinckwitz@germanbreastgroup.de.
Abstract
New insights into neoadjuvant treatment of breast cancer have shown that the prognostic value of pathological complete response has to be rated differently according to subtype. Whereas in triple-negative, HER2-positive (non-luminal) and luminal B (HER2-negative) patients with a pCR after neoadjuvant chemotherapy show a significantly better outcome than patients without a pCR, this prognostic impact cannot be seen in patients with luminal A or luminal B (HER2-positive) tumors. Patients can therefore only avoid an initially high-risk prognosis if they have a pCR of these first mentioned subtypes. For patients with those tumors or with high Ki-67 levels in residual disease, new treatment options have to be found. Contrarily, response-guided chemotherapy, i.e., changing the regimen in case of no early response or intensification in case of early response, showed significant survival advantages only in the latter group. Strategies are currently being developed on how locoregional treatment can be reduced in patients with a pathological complete response. These aim to reduce the extent of surgery or even avoid surgery completely.
PMID: 22890604