Head-to-head comparison of palbociclib and ribociclib in first-line treatment of HR-positive/HER2-negative metastatic breast cancer with real-world data from the OPAL registry. 10. Oktober 2025 Thill M, Zahn MO, Welt A, Nusch A, Zaiss M, Engelken K, Kaltenecker G, Ringwald K, Gratzke K, Dille S, Kruggel L, Jänicke M, Schulz H, Hagen V, Fricker R, Stickeler E, Harbeck N, Wöckel A, Decker T. Int J Cancer. 2025 May 1;156(9):1770-1782. doi: 10.1002/ijc.35296. Epub 2024 Dec 20. PMID: 39707595; PMCID: PMC11887017. Abstract