Rapid and deep prostate-specific antigen (PSA) response to apalutamide plus ADT and survival in metastatic castration-sensitive prostate cancer (mCSPC) in real world practice in the US (OASIS Project).

5076 Background: Apalutamide (APA) in combination with androgen-deprivation therapy (ADT) is an effective life-prolonging treatment option for mCSPC. Early and deep PSA responses are response indicators in metastatic castration-resistant PC that have been associated with improved clinical outcomes in patients with PC. APA+ADT has been shown to induce early and deep PSA responses. We evaluated correlations between PSA and long term clinical outcomes in adults with mCSPC in real world practice. Methods: This retrospective, observational cohort study used the ConcertAI RWD 360 prostate cancer dataset to evaluate correlations between PSA and long term clinical outcomes in adults with mCSPC who initiated treatment with APA+ADT. All patients with newly diagnosed mCSPC from 1 Jan 2018 to 30 Sept 2022 were enrolled and followed up until 31 Mar 2023. Correlations between time to 50% and 90% declines in PSA (PSA50 and PSA90), and time to undetectable PSA (≤0.2 ng/mL) and 24-month OS were evaluated. Adjusted Hazard ratios (aHRs) were estimated using multivariate Cox proportional hazard models adjusted for age, comorbidities, BMI, baseline PSA. Results: 183patients with mCSPC who initiated APA+ADT treatment and had monthly PSA testing were included in the analysis; mean (SD) age 73 years (8), baseline PSA 34 (81). Mean (SD) duration of follow up was 18 m (10). Overall, 116 patients (63%) reached undetectable PSA over the follow-up period and 24-month OS was 68%. OS was significantly higher when patients achieved undetectable PSA, PSA90 and PSA50 within 3 months after initiating APA+ADT (24-month survival rate, 87%, 84% and 80%, respectively) compared with patients who did not reach these levels during the follow-up period (Table). The aHR was 0.15 (95% CI 0.05–0.47; p<0.001) in patients who reached undetectable PSA within 3 months compared with not yet reached. The aHR was 0.27 (0.12–0.65; p<0.01) in patients with onset of undetectable PSA beyond 3 months compared to not reached. Conclusions: Rapid and deep PSA decline was strongly associated with better overall survivalin patients with mCSPC initiated on APA+ADT.Table: see text