Cyclin Dependant Kinase 4/6 (CDK4/6) Inhibitors as a Second Line Treatment in Metastatic Breast Cancer Patients

Breast cancer is the commonest malignancy among females and one of the leading causes of death worldwide. Many drugs have been developed over the years to try to extend survival among these patients including cyclin dependant kinase inhibitors. Cyclin dependant kinase inhibitors (CDK inhibitors) mainly Palbociclib (PAL), ribociclib (RIB) and abemaciclib (ABM) are approved for treatment of hormone receptor positive, HER2 negative advanced breast cancer in the 1st line and subsequent lines in combination with aromatase inhibitors or fulvestrant. Studies showed that they extend progression free survival and recently they showed overall survival benefit. In this study investigators compare Palbociclib+ fulvestrant VS Ribociclib + fulvestrant as a second line treatment in metastatic ER+ve her2 -ve BC in oncology center mansoura university egyptian patients.

Breast cancer is the commonest malignancy among females and one of the leading causes of death worldwide. Many drugs have been developed over the years to try to extend survival among these patients including cyclin dependant kinase inhibitors. Cyclin dependant kinase inhibitors (CDK inhibitors) mainly Palbociclib (PAL), ribociclib (RIB) and abemaciclib (ABM) are approved for treatment of hormone receptor positive, HER2 negative advanced breast cancer in the 1st line and subsequent lines in combination with aromatase inhibitors or fulvestrant. Studies showed that they extend progression free survival and recently they showed overall survival benefit. In this study investigators compare Palbociclib+ fulvestrant VS Ribociclib + fulvestrant as a second line treatment in metastatic ER+ve her2 -ve BC in oncology center mansoura university egyptian patients. The efficacy and comparative toxicity of CDK inhibitors were indirectly compared in a number of trials. Despite differences in inclusion criteria and follow-up length, second-line trials showed similar characteristics.

Unfortunately, despite the similar efficacy and overall response rate (ORR) and a slightly different but near-identical spectrum of adverse events, both agents have not been directly compared with each other. This study aims to fill that gap, and evaluate the toxicity, tolerability and response rate of ribociclib plus fulvestrant versus palbociclib plus fulvestrant, to inform the decision makers.

Eligibility Criteria:
Inclusion Criteria:

* - Pathologically proven diagnosis of adenocarcinoma of the breast with evidence of metastatic disease either progression on adjuvant hormonal or progression on 1st line hormonal for metastatic disease.
* Documentation of ER-positive and/or PR-positive and HER2 negative.
* Prior use of endocrine therapy.
* age \>18 years old.
* ECOG: 0-2
* Postmenopausal is defined as: age\>60 years old or \< 60 years old with cessation off menstruation for at least 12 months and FSH or E2 in postmenopausal range or patients who underwent bilateral oophorectomy.
* Premenopausal is defined if not meeting the criteria of postmenopausal. They are obligated to receive LHRH agonist with their treatment.

Exclusion Criteria:

* - Age \< 18 years old
* Patients with advanced/metastatic, symptomatic, visceral spread(visceral crisis) , that are at risk of life-threatening complications in the short term (including patients with massive uncontrolled effusions \[pleural, pericardial, peritoneal\], pulmonary lymphangitis, and over 50% liver involvement).
* 2nd malignancy other than breast cancer
* ECOG more than 3