REAL LIFE EXPERIENCE OF A CANCER CENTER IN ADVANCED BREAST CANCER USING CYCLIN INHIBITORS

Association of endocrinetherapy and CDK4/6 inhibitors is nowadays the gold standard treatment for endocrine-responsive metastatic breast cancer (mBC), with significant increments in progression free survival and overall survival demonstrated by phase 3 trials, in first and second lines of treatment. In most countries, access to CDK4/6 inhibitors is a challenge, like in Brazil, where even approved by regulatory agency is still not completely incorporated in clinical practice. Real life results of this therapy in estrogen receptor (ER+) mBC is desired. We performed an unicentric, analytic and retrospective study including 114 patients with medical records at AC Camargo Cancer Center between January 1st 2016 and August 15th 2020 of patients with ER+ mBC treated from January of 2016, with endocrinetherapy and CDK4/6 inhibitors (CDK4/6i) 114 patients were included in the study, of which only one (0,87%) was male. The median age at diagnosis was 49,0 years and 19 patients(16,7%) were older than 65. Median age at the beginning of CDK4/6i therapy was 54,5 years. Thirty one patients (27,2%) were stage IV disease and 74 (64,9) received CDK4/6i in combination with fulvestrant or aromatase inhibitor as a first line of mBC treatment, 22 (19,3%) as second line of treatment and 18 (15,8%) as third or subsequent lines of treatment. Seventy four patients (64,9%) received Palbociclib, 29 (25,4%) Ribociclib and 11 (9,6%) Abemaciclib. It is worth mentioning that in 2016, when the drug was first approved in the US, the median time interval in Brazil, from the beginning of treatment with fulvestrant or aromatase inhibitor until the start of ICDK4/6 was 153 days. Because the drug was not yet recognized by Brazilian sanitation authorities its use was dependent on clearance with insurance companies. When the use of this treatment was finally approved in Brazil in 2018 this median interval dropped to 43 days, and to 27 days in 2020. Until the closing of the database in August 15, 2020, the median for progression free survival (PFS) was not reached for patients receiving treatment as a first line. For those receiving treatment as a second line the median PFS was 14.9 months and after third and subsequent lines was 7.4months. At the time of data collection, after a median time of follow up of 13,5 months there were 19 deaths, one of which was due to secondary acute myeloid leukemia. The median overall survival time was not reached in first or second lines of treatment.