Clinical Outcomes of Patients Treated with Ribociclib in Combination with Aromatase Inhibitors or Fulvestrant for HR-Positive, HER2-Negative Metastatic Breast Cancer, Real-World Data from a Low-Resourced Country

Hikmat Abdel-Razeq,1,2 Baha Sharaf,1 Suhaib Khater,1 Huda Jafar Baidoun,2 Hira Bani Hani,1 Ayat Taqash,3 Osama El Khatib,1 Sarah Edaily,1 Mahmoud Abunasser,1 Faris Tamimi,1 Yosra Nabeel Al-Masri,1 Tamer Moh’d Waleed Al-Batsh,1 Anas Zayed,1 Tala Ghatasheh,1 Tala Radaideh1 1Department of Internal Medicine, Section of Hematology and Medical Oncology, King Hussein Cancer Center, Amman, Jordan; 2School of Medicine, the University of Jordan, Amman, Jordan; 3Office of Scientific Affairs and Research. King Hussein Cancer Center, Amman, JordanCorrespondence: Hikmat Abdel-Razeq, Department of Internal Medicine, Section of Hematology and Medical OncologyKing Hussein Cancer Center, 202 Queen Rania Al Abdullah Street, P.O. Box: 1269, Amman, 11941, Jordan, Tel: +962-6 5300460, Email habdelrazeq@khcc.joBackground: Cyclin-dependent kinase (CDK) 4/6 inhibitors have revolutionized the treatment landscape of hormone receptor-positive (HR+) and human epidermal growth factor receptor 2-negative (HER2 −) metastatic breast cancer (MBC). Here, we present the real-world clinical outcomes and toxicity data of patients treated at a single cancer center.Methods: A retrospective analysis was conducted on patients with HR+/HER2− MBC treated with ribociclib plus endocrine therapy (ET). Outcomes measured included progression-free survival (PFS), overall survival (OS), and adverse events.Results: A total of 356 patients (median age 52, range 27– 91 years) were enrolled, all with metastatic disease; 204 (57.5%) had de novo metastasis, and 183 (51.4%) had visceral metastasis. Ribociclib was combined with aromatase inhibitors in 321 patients (90.2%) and with fulvestrant in 35 patients (9.8%). Dose reduction was needed in 101 patients (28.4%), primarily due to neutropenia (21.3%) and abnormal liver enzymes (5.9%). After a median follow-up of 36.3 months, median PFS was 27.3 months (95% CI: 21.3– 31.7). PFS was significantly better in patients receiving ribociclib as first-line therapy (32.1 months, 95% CI: 27.7– 42.1, p < 0.0001) and those with non-visceral metastasis (38.6 months, 95% CI: 29.8–NR, p < 0.0001). Similarly, OS was significantly better in first-line treatment (48.6 months, 95% CI: 39.1–NR) and non-visceral metastasis cases (NR, 95% CI: 40.6–NR, p < 0.0001). No significant differences in 3-year PFS and OS were found between patients with and without dose reductions.Conclusion: In real-world settings, and away from the stringency of controlled clinical trials, endocrine therapy in combination with ribociclib in patients with HR-positive/HER2-negative MBC is an effective and well-tolerated therapy with a manageable toxicity profile and a low drug discontinuation rate. Dose reduction due to toxicity did not worsen the outcome.Keywords: metastatic breast cancer, MBC, CDK4/6 inhibitors, ribociclib, aromatase inhibitors, fulvestrant