233P Real-world first-line (1L) treatment selection for Australian patients (pts) with hormone receptor-positive advanced breast cancer (HR+ ABC)

CDK4/6 inhibitor (CDK4/6i) plus endocrine therapy (ET) is now standard 1L treatment for HR+ ABC. Whilst landmark trials demonstrate improvement in survival outcomes, real world treatment patterns and toxicities are limited. ARORA, a multi-site Australian registry, captures real-world data on pts with HR+ ABC including baseline characteristics, systemic therapy sequencing and treatment outcomes. Consecutive pts diagnosed between Jan 2020 and Jan 2024 were enrolled. Data from 438 HR+ ABC pts with median follow up of 24.3 months were analysed. Median age was 64 yrs (IQR 54-74), with 64% ECOG 0-1 and 42% Charlson comorbidity index (CCI) ≥3. 44% of pts had visceral metastases and 19% had bone-only metastases at diagnosis. 60% of pts had relapsed disease at a median time of 7.0 yrs (IQR 4.2-10). Of relapsed pts, 10% and 48% received neoadjuvant and adjuvant chemotherapy (CT) respectively, and 79% received adjuvant ET. 41% relapsed on or within 12 months of stopping adjuvant ET. Of the 426 (97%) HR+ ABC pts who received 1L treatment, 77% had CDK4/6i + ET, 14% ET alone, 5% CT and 5% CT then ET +/- CDK 4/6i. CDK4/6i selection was 46% palbociclib (PA), 35% ribociclib (RI), 13% abemaciclib (AB). Compared to pts who received 1L CDK4/6i+ET, pts who received 1L ET alone were older (78.5 vs 63.0 yrs, p<0.01), with poorer performance status (ECOG ≥ 2 62% vs 30%, p<0.01) and more comorbidities (CCI ≥3 60% vs 37%, p<0.01), but with no difference in visceral metastases (42% vs 41%, p=0.99). Common CDK4/6i related toxicities were diarrhoea (PA 10% vs RI 12% vs AB 73%), neutropenia (PA 65% vs RI 47% vs AB 23%) and nausea/vomiting (PA 24% vs RI 47% vs AB 30%). 54% pts remain on 1L treatment, 27% and 21% have ceased due to progression and toxicity/pt preference respectively. Pts who received 1L CDK4/6i+ET had longer PFS than pts that received ET alone (30.4 vs 21.9 months, HR 0.58, p=0.02). Reflecting international guidelines, the majority of routine care Australian HR+ ABC pts receive 1L CDK4/6i + ET. Pt factors such as age, ECOG and comorbidities appear to impact treatment selection. Real world CDK4/6i toxicity and early PFS data are similar to those reported in landmark clinical trials.