Palbociclib in the Treatment of HR+/ HER2‐ Advanced or Metastatic Breast Cancer in Australia: A Real‐World Retrospective Analysis

ABSTRACT Background There is limited real‐world data on the use of CDK4/6 inhibitors in Australian patients with HR+/HER2‐ advanced or metastatic breast cancer. This study describes the demographic and clinical characteristics of patients initiating CDK4/6 inhibitors, and analyses of real‐world treatment patterns and outcomes with palbociclib, including dose modifications, time to chemotherapy initiation, and duration of treatment. Methods This non‐interventional retrospective cohort study from Australia used the Pharmaceutical Benefits Scheme dataset, which includes longitudinal claims data from January 2004 to December 2023. The study population comprised CDK4/6i‐naïve patients aged ≥ 18 years initiating first treatment with a CDK4/6 inhibitor between June 2018 and December 2023. Comorbidities were determined using the validated Rx‐Risk Comorbidity Index. Descriptive data analyses were conducted, and the Kaplan–Meier method was used for time‐to‐event analyses. Results The study analyzed data from 1128 patients, including 407 initiating palbociclib. The median age at palbociclib initiation was 67 years, with 67% aged > 60 years. Sixty seven percent of patients had received treatment for ≥ 3 comorbidities in the preceding 12 months. 80% of patients started on the 125‐mg formulation, and 53% did not undergo a dose modification (all initiated doses). At a median follow‐up of 38 months, 61% and 40% remained on treatment with palbociclib at 12 and 24 months, respectively. Median duration of treatment was 541 days (18 months) and median time to chemotherapy was not reached. Conclusions This study provides real‐world data on the utilization and outcomes of palbociclib in Australia, complementing data from randomized clinical trials and offering insights into the management of HR+/HER2‐ advanced or metastatic breast cancer. Trial Registration ClinicalTrials.Gov identifier: NCT06624020