Adjuvant treatment in hormone receptor-positive early breast cancer: New approaches of endocrine therapy

Breast cancer is the most common cancer in women, and luminal breast cancer is the predominant subtype, characterized by the presence of estrogen receptors and/or progesterone receptors in tumor cells. Adjuvant endocrine therapy is the pivotal approach in the management of luminal early breast cancer. Hence, new therapeutic approaches have been studied during the last few years, especially in patients with high risk of recurrence.Here we provide a summary of the most recent clinical trials evaluating adjuvant treatment in hormone-receptors-positive early breast cancer. First, the main cornerstone is related to the role of extended endocrine treatment, which has been widely investigated to access a benefit in disease-free survival and overall survival (only the GIM4 trial has positive feedback about survival) and to tailor the treatment according to patient compliance. The results highlighted an advantage in extending the use of endocrine treatment for at least seven full years, considering aromatase inhibitors as principal drugs. Second, the shift of CDK4/6 inhibitors (CDK4/6i) from advanced to early setting reported positive outcomes, with favorable results from MonarchE and NATALEE trials, using Abemaciclib and Ribociclib respectively, even if non-negligible toxicities have been reported. Last, the use of PARP inhibitors for BRCA1/2 mutated patients has been evaluated in the OlympiA trial (Olaparib), observing a comparable benefit between hormone-receptors-positive and triple-negative early breast cancer.However, more data are still required to better select patients that could benefit more from CDK4/6i considering side effects too, and sequential treatments are still not codified.