To assess CDK4/6i toxicity and effect on PFS in the Egyptian population

Inclusion Criteria:

• Breast cancer patients aged 18 years old or more
• Female patients
• Histologically proven invasive breast cancer
• Histologically proven HR-positive and HER2-negative breast cancer
• Metastatic breast cancer (Stage 4 according to AJCC 8th edition 2017)
• Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0 to 3.
• Adequate hematological and organs function
• Patients receiving CDK 4/6 inhibitor combined with endocrine therapy(Aromatase inhibitors , GnRH agonists, fulvastrent). as a first or second line treatment

Exclusion Criteria:

• - Male breast cancer patients
• Patients in, visceral crisis (defined as : severe organ dysfunction, as assessed by signs and symptoms, laboratory studies and rapid progression of disease ) that are at risk of life threatening complication in the short term.
• Prior treatment with any CDK 4/6 inhibitor.
• History of any other cancer , unless in complete remission with no therapy for a minimum of 3 years.
• Have active bacterial or fungal infection, or detectable viral infection.

Breast Cancer patients attending Ain Shams University Clinical Oncology and Nuclear Medicine Department breast clinic from July 2022 till December 2024