268P - Results from a real-world study of patients (pts) with hormone-receptor (HR)-positive HER2-negative metastatic breast cancer (MBC) treated with CDK4/6 inhibitors (CDK 4/6i) in three institutions

Background

CDK 4/6i combined with endocrine therapy have become the gold standard in HR-positive HER-negative MBC treatment. Pts included in randomized clinical trials (RCT) are often not representative of real population. Real word data (RWD) can be used to confirm reproducibility of evidence from RCTs in routine clinical practice. We report results from retrospective analysis of a RWD cohort of pts.

Methods

Clinical-pathological data of R-positive HER2-negative MBC pts treated between January 2017 and December 2020 in 3 institutions in Spain (Institut Català d’Oncologia L’Hospitalet, Badalona and Girona) were retrospectively collected. The primary goal was to assess progression free survival (PFS), overall survival (OS) and safety.

Results

331 pts were included with a median follow-up of 21.9 months (m) (IQR: 11.7-32.5). 73.7% were treated with Palbociclib (P), 15.7% with Ribociclib (R) and 10.6% with Abemacicilib (A). Median age was 62 years (y) (52.0-71.0), being 15.7% ≥75y. 73.7% were diagnosed with recurrence disease, 77% of cases had bone metastases whereas 50% had visceral metastases (hepatic and/or lung).1^st line (L) therapy was prescribed in 66.5% of cases, 2^ndL in 21.1% and 3^rdor later line in 11.4% . At the date of administrative censoring (1^st December 2021), 42.7% remained progression-free, being a stable disease the most frequent radiological response. mPFS was 21.8m (16-36.2) in 1^stL, 9.6m(6.1-14.6) in 2^nd L and 11.5m (7.9-18.5) in 3^rd L. mOs was not reached for 1^st and 2^ndL and was 27.3m (95% CI: 22.1-NR) in 3^rd L. In elderly pts (≥75y), mPFS was 27.2m (11.2-NR) in 1^stL, 4.1m (3.1-NR) in 2^nd L and 10.5m (7.3, NR) in 3^rd L.

Most common adverse event was neutropenia, being grade (G) ≥3 in 51.3% of pts. 10.3% of R pts had G ≥3 hepatotoxiciy (no cases in P and A groups). 55% of pts needed dose reductions (DR) and 17.3% stopped treatment due to toxicity. No differences in mPFS were found on pts who had DR.

Conclusions

This real-world-data with CDK 4/6i provides data in terms of clinical outcomes, effectiveness, and toxicities in our daily practice in three institutions. Age ≥75y and DR are not associated with lower mPFS.

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

B. Cirauqui Cirauqui: Financial Interests, Personal, Invited Speaker: BMS; Financial Interests, Personal, Other, Training grant: MSD, BMS; Non-Financial Interests, Member, Board of directors: TTCC group; Non-Financial Interests, Member: GEICAM, SOLTI, SEOM. V. Quiroga Garcia: Financial Interests, Personal, Advisory Board: ROCHE; Financial Interests, Personal, Invited Speaker: Novartis; Non-Financial Interests, Other, Member: GEICAM, SOLTI; Non-Financial Interests, Other, Menber: SEOM. S. Pernas Simon: Financial Interests, Personal, Advisory Board: SeaGen, AstraZeneca- Daiichi Sankyo, Pierre-Fabre; Financial Interests, Personal, Invited Speaker: Lilly, Novartis, Eisai, Roche; Financial Interests, Institutional, Invited Speaker: Astra-Zeneca, Novartis, Daichii-Sankyo. E. Felip: Financial Interests, Personal, Advisory Board: Novartis; Financial Interests, Personal, Speaker’s Bureau: GEICAM; Financial Interests, Personal, Other, Congress fee: Pfizer, Lilly; Non-Financial Interests, Personal, Member: GEICAM, SOLTI. All other authors have declared no conflicts of interest.