Palbociclib Combined With an Aromatase Inhibitor in Breast Cancer
Palbociclib Combined With an Aromatase Inhibitor in Breast Cancer
Pfizer's innovative drug palbociclib (trade name: Ibrance®) got China National Drug
 Administration (CNDA) approval on July 31, 2018. Palbociclib combined with an aromatase
 inhibitor can be used to treat hormone receptor-positive/human epidermal growth factor
 receptor 2-negative locally advanced breast cancer or metastatic breast cancer. This brings
 more treatment options for hormone receptor-positive/human epidermal growth factor receptor
 2-negative locally advanced breast cancer. How to scientifically evaluate the efficacy,
 tolerability, and safety of palbociclib combined with an aromatase inhibitor and to establish
 a more suitable treatment strategy for Chinese patients is one of the questions that need to
 be answered in clinical practice. This multi-center parallel-group randomized controlled
 trial will address on this issue.
Breast cancer is one of the most common cancers in women. Once advanced, it is usually not
 cured. Studies have shown that patients with advanced breast cancer have a median survival of
 2-3 years. For inoperable locally advanced breast cancer, systemic therapy is the first
 choice of treatment. Systemic treatments of hormone receptor-positive/human epidermal growth
 factor receptor 2-negative breast cancer mainly include endocrine monotherapy, multi-drug
 combination therapy and chemotherapy. The overall survival is similar between patients with
 hormone receptor-positive/human epidermal growth factor receptor 2-negative breast cancer
 receiving chemotherapy and those receiving endocrine therapy. But quality of life and
 progression-free survival of patients receiving endocrine therapy are superior to those of
 receiving chemotherapy. Therefore, both the National Comprehensive Cancer Network (NCCN) and
 the 2018 Chinese Expert Consensus on the Clinical Diagnosis and Treatment of Advanced Breast
 Carcinoma guidelines confirm that endocrine therapy is the preferred treatment for hormone
 receptor-positive/human epidermal growth factor receptor 2-negative breast cancer.

 Palbociclib is a cyclin-dependent kinase (CDK) 4/6 inhibitor that reduces the proliferation
 of estrogen receptor-positive breast cancer cells by blocking cells from the G1 phase to the
 S phase. Pfizer's innovative drug palbociclib (trade name: Ibrance®) was approved by the
 China National Drug Administration on July 31, 2018 for the treatment of hormone
 receptor-positive/human epidermal growth factor receptor 2-negative locally advanced breast
 cancer or metastatic breast cancer. In addition, aromatase inhibitors such as letrozole
 (trade name: Femara ®) can prolong the progression-free survival in the first-line therapy
 for advanced breast cancer to 10-13 months. Palbociclib combined with letrozole has been
 shown to exhibit stronger inhibitory effects on phosphorylation of retinoblastoma gene (Rt),
 downstream signaling and tumor growth than monotherapy. Since 2015, palbociclib combined with
 letrozole has been recommended by the NCCN guideline as one treatment option for advanced
 breast cancer. However, since palbociclib has been approved for market entry in China for
 only 1 year, little is reported in China regarding large-sample clinical trials regarding the
 efficacy, tolerability, and safety of palbociclib combined with an aromatase inhibitor in
 hormone receptor-positive/human epidermal growth factor receptor 2-negative locally advanced
 breast cancer.
Inclusion Criteria:

 -  Patients with histological and imaging findings-confirmed hormone
 receptor-positive/human epidermal growth factor receptor 2-negative breast cancer;

 -  postmenopausal patients;

 -  eligible patients receiving one or more treatment strategies who are followed up in
 the center where they receive treatment;

 -  provision of written informed consent.

 Exclusion Criteria:

 -  Age < 18 years;

 -  pregnant woman;

 -  participating in other clinical trials.