Abstract PO4-12-12: An Updated analysis of risk factor identification and Hyperglycemia prevention with alpelisib + fulvestrant in PIKC3A-mutated, hormone-receptor positive, human epidermal growth factor-2 negative advanced breast cancer

Abstract Background: SOLAR-1 investigated use of alpelisib (ALP) + fulvestrant (FLV) in patients (pts) with hormone-receptor positive (HR+)/human epidermal growth factor-2 negative (HER2-), PIK3CA-mutated advanced breast cancer (ABC) after progression on endocrine-based therapy and demonstrated a clinically significant increase in all-grade (G) and G3-4 hyperglycemia (HG) compared to placebo + FLV. Current guidance recommends an insulin sensitizer (metformin, thiazolidinedione, SGLT2i) at HG onset. Given high rates of HG, a preventative protocol and identification (ID) of associated risk factors (RFs) was implemented to minimize HG, dose reductions and discontinuation. Although METALLICA investigated the implementation of metformin for hyperglycemia prophylaxis, there is limited data for alpelisib use and hyperglycemia prevention in high risk or controlled type 2 diabetic patients. Duke Breast Oncology Clinic (DBOC) implemented a preventive strategy to minimize HG and treatment disruptions in patients receiving alpelisib, including pre-diabetic and controlled-diabetic patients. Methods: This single-center, retrospective study included pts receiving at least one 28-day cycle of ALP+FLV between June 2019 and April 2023. One week prior to ALP initiation, pts initiated an insulin-sensitizer. Pts had fasting plasma glucose (FPG) levels drawn on day 8, 15, 28, and monthly while on ALP. The primary outcome was incidence of G2-4 HG. Descriptive statistics were used to summarize results. Number of RFs for HG (age ≥ 65 years, BMI ≥ 25 kg/m2, baseline FPG ≥ 100 mg/dL, and A1c ≥ 5.7%) were compared between pts with and without HG using Wilcoxon rank-sum test. Results A total of 30 pts (29 females; 1 male) were included with a median age of 60 years. The cohort was 70% White, 23% Black, while 67% were overweight/obese, and 50% had a history of type 2 diabetes mellitus (T2DM), gestational diabetes, or pre-diabetes. 29 pts received a CDK4/6 inhibitor prior to starting ALP. By day 28, 13 pts (43%) had G2-4 HG, with only 4 (13%) having G3 HG and zero having grade 4. Pts with G2-4 HG had a median of 2 RFs compared to only 1 RF if no HG. 8 pts (27%) required a temporary hold of ALP and 5 pts (17%) required a dose reduction in ALP due to HG. 25 pts permanently discontinued ALP; 14 due to disease progression and 8 due to an adverse event with only 3 due to HG. Median duration of ALP was 86 days (range 24-442), with 5 pts continuing to receive ALP at time of analysis. Patients with grade 2-4 HG by day 28 after ALP initiation had an older median age (66 years), higher BMI (median 28.1 kg/m2), higher baseline FPG (median 100 mg/dL), and higher baseline HbA1c (median 5.6%) compared to those without grade 2-4 HG (Table). Conclusions: Implementation of a HG prevention protocol with ALP in the real-world setting demonstrated fewer G3-4 HG events compared to that seen in SOLAR-1 (13% vs 36.6%) but slightly higher than METALLICA (6%) although we included a higher risk patient population. An increase in HG-associated RFs correlated with a higher incidence of G2-4 HG. Early risk identification and optimization of prophylactic antihyperglycemics can reduce ALP dose reductions and discontinuations secondary to HG. ALP use in higher-risk patients can be considered with a HG prevention protocol. Table 1. Hyperglycemia outcomes Citation Format: Heather Moore, Sarah Burnette, Emily Poehlein, Hui-Jie Lee, Kelly Westbrook, Thomas Bagwell, Kervin Novido, Susan Dent. An Updated analysis of risk factor identification and Hyperglycemia prevention with alpelisib + fulvestrant in PIKC3A-mutated, hormone-receptor positive, human epidermal growth factor-2 negative advanced breast cancer abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-12-12.