The investigators will have a six-month recruitment period to include the eligible subjects as per the protocol selection criteria. Retrospective patients should have been on Ribociclib in combination with hormonal therapy for at least 18 months and stopped the medication before the patient's recruitment.
Ambispective patients should have initiated Ribociclib, in combination with hormonal therapy, for at least 12 months before the patient's recruitment date and are still on Ribociclib in combination with hormonal therapy at recruitment. These patients will be followed up till progression, death, Ribociclib discontinuation due to adverse events, or till a maximum period of 6 months, whichever comes first.
Data will be collected from patient electronic medical records in the sites chosen for patients who received Ribociclib, in combination with hormonal therapy, in the first or second-line setting available in the relevant institutions.
A total of 550 patients is planned for this study. The planned sample size should capture very common adverse events reported in previous studies as well as adverse events ≥ 10% occurring in grade 3 and grade 4 with precision ±2.5%.
