Preoperative endocrine therapy as a predictive biomarker of adjuvant chemotherapy

Abstract

Patients with early breast cancer (stage I‐IIIA) usually receive adjuvant systemic therapy due to prevent recurrence after surgery. Treatment strategies are determined based on molecular subtypes and baseline risk. In practice, investigators provide the best strategy for individual patients based on risk benefit balance according to clinical, pathological factors and multigene signature. However the appropriateness of chemotherapy for luminal breast cancer has been an important clinical issue during ten years and we don't have clear answer. We conducted randomized phase III trials as called New primary Endocrine therapy Origination Study (NEOS) in luminal breast cancer patients about ten years ago. NEOS has been performed at multicenter in Japan since Jun 2008. NEOS is evaluated with or without chemotherapy in patients with postmenopausal breast cancer that has responded to preoperative endocrine therapy. The aims of this trial are toj define patients who might not require chemotherapy by using their response to preoperative endocrine therapyj analyze the relationship between preoperative endocrine therapy and long‐term prognosisj and analyze the correlation between clinical and pathologic response to preoperative endocrine therapy with additional adjuvant chemotherapy. Multigene profiling kits such as Oncotype DXVR and MammaPrintVR have been used in trials (TAILORx in North America and MINDACT in Euro, respectively) conducted outside of Japan in an attempt to prospectively identify patients likely or unlikely to benefit from adjuvant chemotherapy. Already some parts of TAILORx and MINDACT trial data were published Nov 2015 and Aug 2016 respectively. However these gene screening kits are not widely used because of high cost without health insurance covered in Japan. Therefore, response to preoperative endocrine therapy may become a very useful tool in practice if it can help to determine the appropriate postoperative treatment regimen.