The ATLANT study is prospective, multicentre, non-interventional, observational study. Patients with HR+/HER2-negative metastatic breast cancer received abemaciclib as monotherapy or in combination with endocrine therapy.

The ATLANT study is prospective, multicentre, non-interventional, observational study.

136 patients with HR+/HER2-negative metastatic breast cancer received abemaciclib as monotherapy or in combination with endocrine therapy in different line therapy.

The purpose of this study is to better understand how abemciclib combinations are used in real-life conditions and their clinical impact for the treatment of Russian patients affected by (HR+)/ (HER2-) advanced breast cancer (ABC) or metastatic breast cancer (MBC).

Inclusion Criteria:

1. Age ≥18 years
2. Patients must have a diagnosis of HR+ breast cancer. To fulfill the requirement of HR+ disease, a breast cancer must express, by immunohistochemistry (IHC), at least one of the hormone receptors (ER, progesterone receptor [PgR]) as defined in the relevant American Society of Clinical Oncology/College of American Pathologists Guidelines: For ER and PgR assays to be considered positive, ≥1% of tumor cell nuclei must be immunoreactive by immunohistochemistry (IHC)
3. Patient has HER2-negative breast cancer defined as a negative in situ hybridization test or an IHC status of 0, 1+ or 2+. If IHC is 2+, a negative in situ hybridization (FISH, CISH, or SISH) test is required by local laboratory testing.
4. Patients with advanced (loco-regionally recurrent, or metastatic) breast cancer not amenable to curative therapy.
5. WHO performance status of 0-2
6. The patient has adequate organ function
7. Any number of prior therapies (including none) is permitted
8. Рatients who will start Abemaciclib as a Single Agent or in combination with endocrine therapy

Exclusion Criteria:

1. Uncontrolled intercurrent illness including, but not limited to, known ongoing or active infection, including HIV, active hepatitis B or C, symptomatic congestive heart failure, unstable angina pectoris, cardiac arrhythmia (specifically, atrial fibrillation or ventricular dysrhythmias except ventricular premature contractions), or psychiatric illness/social situations that would limit compliance with study requirements.
2. Participants must not be pregnant or breastfeeding

Patients with histologically confirmed HR-positive, HER2-negative breast cancer treated with abemaciclib in combination with endocrine therapy or as a single agent