CDK4/6 Inhibitors (CKD4/6i) in advanced hormone-receptor-positive (HR+) HER2-negative (HER2-) breast cancer: Prescribing practices and outcomes in a real-world, Australian cohort

Abstract

Aims: To examine treatment trends, efficacy and toxicity in advanced HR+/HER2- breast cancer in a real-world, Australian cohort. Method(s): Data was extracted from the Advanced Hormone Receptor Positive Breast Cancer Registry in Australia (ARORA), a prospective registry, including 15 sites. Patients had inoperable or metastatic HR+/HER2- breast cancer diagnosed after January 1st 2020. Patient and disease characteristics, treatment, progression-free survival (PFS) and adverse events (AEs) were extracted. Data analysis used descriptive statistics. This Research Collaboration was supported by Novartis. Result(s): Two hundred and one patients were enrolled; six were excluded due to incomplete data; median age 63 years (29-89 years); median follow-up 12.8 months. Sixty-seven (34%) had de novo metastatic disease. Of 128 patients with relapsed disease, 107 (84%) received adjuvant therapy, 98 (77%) endocrine therapy (ET) and 69 (54%) chemotherapy. Seventeen (13%) received no adjuvant therapy. Four (3%)were unknown.Onehundred and forty-seven (75%) received CDK4/6i+ET in the first-line metastatic setting, 25 (13%) received ET alone, 13 (7%) received chemotherapy and nine (5%) received no treatment. In the CDK4/6i+ET group, 83 (56%) received Palbociclib, 58 (39%) Ribociclib and 12 (8%)Abemaciclib.CDK4/6i was combinedwith an aromatase inhibitor in 121 (82%) and with fulvestrant in 27 (18%). Sixty-seven (46%) in the CDK4/6i+ET group had visceral metastases, compared to nine (69%) in the chemotherapy group. At reporting, 55 (27%) had progressed on first-line treatment; of these 43% had relapsed on or within 6 months of adjuvant ET and 27% had de novo metastatic disease. Twelve-month PFS was 83% for CDK4/6i+ET. PFS and OS data is immature. The most common AEs associated with CDK4/6i+ET were neutropenia (27%), nausea/vomiting (14%) and diarrhoea (5%). Conclusion(s): Real-world Australian data of advanced HR+/HER2- breast cancer demonstrates significant uptake of CDK4/6i+ET in the first-line setting. Toxicity is consistent with previous reports. Longer follow up will allow analysis of efficacy and subgroups.