Study to Assess the Safety and Efficacy of Ribociclib (LEE011) in Combination With Letrozole for the Treatment of Men and Pre/Postmenopausal Women With HR+ HER2- aBC

The purpose of this study is to collect additional safety and efficacy data for the combination of ribociclib + letrozole in men and pre/postmenopausal women with HR+HER2- advanced breast cancer and no prior hormonal treatment for advanced disease..

This was an open-label, single arm, multi-center Phase IIIb study. The study was composed of 2 phases: Core Phase and Extension Phase. In the Core Phase, safety and efficacy data was collected. The study treatment during the Core Phase was provided until disease progression, death, unacceptable toxicities, physician's decision, subject/guardian's decision, protocol deviation, study termination by sponsor, lost to follow-up, technical problems or up to 18 months after LPFV. In the event that patients were still deriving benefit at the end of the Core phase and ribociclib was not approved or available and reimbursed, patients were transitioned to the Extension Phase and continued to receive study treatment until progression, intolerance, death or physician/patient decision. Only safety and clinical benefit (as assessed by investigator) data was collected in the Extension Phase. During the Extension Phase, if ribociclib became locally approved and reimbursed, patients were to be transitioned to prescription. Patients who completed the Extension Phase and continued to derive clinical benefit from the treatment based on the investigator's evaluation received ribociclib from prescription (if approved and reimbursed), another post-trial access program, or other drug access/support program(s). Canadian sub-study: this sub-study was a multicenter Canadian exploratory correlative sample collection sub-study that aimed to better understand mechanisms of response and resistance to ribociclib in combination with letrozole therapy. This sub-study was available for all Canadian subjects enrolled on the main study and did not alter the planned treatment.