Primary endocrine therapy is an option in cases of hormone receptor positive and HER2
negative non-metastatic breast cancer. Aromatase inhibitors are considered the therapy of choice in
postmenopausal patients. In premenopausal patients aromatase inhibitors in combination with LHRHanalogues
are regarded superior to tamoxifen.
Three different settings have to be discriminated:
• Patients too frail for surgery are candidates for primary endocrine therapy in order to control the
disease. Treatment duration is determined by the course of the disease.
• Patients with tumors not operable in general or not operable by breast conserving therapy but not
fit for or with relative contraindications to chemotherapy either are candidates for neoadjuvant
endocrine therapy in order to achieve downstaging. Treatment duration should be at least 6
months and probably not longer than 12 months with the individual duration depending on the
experience and skills of the breast surgeon.
• Patients in whom the indication for chemotherapy is uncertain due to an intermediate risk neoadjuvant
endocrine therapy may undergo endocrine therapy in order to perform in vivo sensitivity
testing. Treatment duration should be at least 3 months up to 6 months according to current data.
Data from retrospective analyses show that short-term on-treatment assessment of Ki67 by rebiopsy
or postoperative assessment of the PEPI score may identify low risk groups with no meaningful
expected benefit from additional chemotherapy.
In order to retrieve more detailed recommendations, results of ongoing prospective trials have to be
awaited. Data regarding on-treatment genomic testing are promising but immature for clinical practice
as of yet.