Abstract
Estrogen receptor positive breast neoplasias represent over 70% of diagnosed breast cancers. Depending on the stage at which the tumor is detected, HER2 status and genomic risk, endocrine therapy is combined with either radio, chemo and/or targeted therapy. A growing amount of evidence supports the notion that components of the tumor microenvironment play specific roles in response to treatment and that strategies targeting these key interactions with tumor cells could pave the way to a new generation of therapies. In this review, we analyze the evidence suggesting different components of the tumor microenvironment play a role in hormone receptor positive breast cancer progression. In particular we focus on the immune system, carcinoma associated fibroblasts and the extracellular matrix. Further insight into the cross talk between these constituents of the microenvironment and the tumor cells may lead to therapies that eliminate disseminated metastatic cells early on, and thus reduce distant disease relapse which is the leading cause of death for patients who are diagnosed with this illness.
Highlights
Breast cancer is the most frequent cancer in women in the western world; one in eight women will have breast cancer at some point in their life [1]
A growing body of evidence supports the notion that components of the tumor microenvironment play specific roles in response to therapy and that strategies targeting the interactions established with tumor cells could pave the way to a new generation of therapies
The current management of ER+ breast cancer is based on how far the disease has progressed at the time of diagnosis, HER2 status and genomic risk leading to treatments that include chemotherapy, endocrine therapy, and targeted therapy [6]
Summary
Breast cancer is the most frequent cancer in women in the western world; one in eight women will have breast cancer at some point in their life [1]. Seventy-five percent of diagnosed breast tumors express estrogen receptor-alpha (ERα) and endocrine therapy is the treatment of choice for patients with tumors of these characteristics. Within the scope of endocrine therapies, tamoxifen, a selective estrogen receptor modulator (SERM), has been the most widely used over the last 30 years [2]. Depending on the stage at which the tumor is detected, HER2 status and genomic risk, endocrine therapy is combined with either radio, chemo and/or targeted therapy [4]. Patients with ER+ early stage breast cancer are susceptible to late recurrence that can take place even after 15 years of treatment interruption. The best outcomes with extended therapy in patients with a high risk of relapse are found in those who have received 5 years of tamoxifen and up to 3 years of an AI [5, 6]
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