Study in Women With Advanced Breast Cancer Receiving Palbociclib With AI or Fulvestrant

This is a prospective, open-label, multi-center, single arm, non-comparative phase II study in women with HR+/HER2- advanced breast cancer receiving palbociclib in addition to an aromatase inhibitor or fulvestrant. The study will take place in Germany (85 study centers). In total, 360 patients will be enrolled in this study. 6 treatment groups are planned. The study seeks to recruit 60 (58-62) patients per recruitment group. For first-line treatment with palbociclib - and letrozole (Enrollment Group 1), anastrozole (Enrollment Group 2), exemestane (Enrollment Group 3) or fulvestrant (Enrollment Group 4) and 60 (58-62) patients for second- or later-line treatment with palbociclib -and letrozole (Enrollment Group 5) or fulvestrant (Enrollment Group 6). Recruitment will be centrally monitored to allow closure of a respective group as soon as 60 (58-62) patients have been enrolled. Treatment will be continued until disease progression, intolerable toxicity, death or any other reason. In case a combination partner is discontinued, palbociclib has to be discontinued. In case treatment with palbociclib is stopped, combination partner can be continued according to investigator's discretion. Irrespectively of the combination partner, the discontinuation of palbociclib is defined as end of treatment (EOT) in this study. After EOT the patient enters the follow-up period. Primary end point is clinical benefit rate 24 weeks after the first study treatment of the patient. A study independent, decentral, "virtual" biobank will be established. All patients will be asked to give consent for their tumor samples to be used for future investigational research. Study sites will inform the local pathologists about the patient's consent and ask for the tissue sample to be reserved for future analyses. The site is requested to collect contact details of the pathologist storing the tumor sample, the sample's identification number(s), and to document these in the eCRF. The decision to perform subsequent investigational research studies on collected samples will be based on outcome data from this study or from new scientific findings related to the drug class or disease, as well as reagent and assay availability.