First-line maintenance olaparib in a low–body mass index Asian population with advanced ovarian cancer: Real-world outcomes from a Vietnamese cohort.

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Background: Patients enrolled in pivotal poly(ADP-ribose) polymerase (PARP) inhibitor trials predominantly represent Western populations with relatively higher body mass index (BMI), whereas Asian patients typically present with substantially lower BMI. Whether this difference influences the effectiveness and tolerability of fixed-dose olaparib remains uncertain. We evaluated real-world outcomes of first-line maintenance olaparib in a Vietnamese cohort characterized by predominantly low BMI. Methods: This retrospective cohort study included patients with FIGO stage III–IV ovarian cancer treated at Vietnam National Cancer Hospital who received first-line maintenance olaparib with or without bevacizumab between 2021 and 2025. BMI at treatment initiation was analyzed as a continuous variable and categorized using Asian BMI criteria (< 23 vs ≥23 kg/m²). Progression-free survival (PFS) and overall survival (OS) were estimated using Kaplan–Meier methods, and toxicities were graded according to CTCAE v5.0. Results: Thirty-two patients were included. The mean age was 54.9 ± 10.0 years (range 39–74). Median BMI was 22.1 kg/m², and 68.8% of patients had BMI < 23 kg/m², and 62.5% had BRCA1/2 mutations. At a median follow-up of 24 months, 12- and 24-month PFS rates were 85.2% and 78.7%, respectively, while corresponding OS rates were 95.7% and 90.0%. Patients with BRCA mutations demonstrated significantly superior 24-month PFS compared with HRD-positive, BRCA–wild-type patients (91.7% vs. 59.5%, p = 0.008). Treatment-related toxicities were manageable and did not increase among lower-BMI patients. Dose reduction and discontinuation occurred in 25.0% and 3.1%, respectively. Grade ≥3 anemia occurred in 15.6%, with similar rates between BMI < 23 and ≥23 groups (13.6% vs. 20.0%). Conclusions: In this real-world LMIC cohort with predominantly low BMI, first-line maintenance olaparib demonstrated effectiveness and safety comparable to pivotal trials conducted in higher-BMI Western populations.