Apalutamide and Stereotactic Body Radiotherapy in Metastatic Hormone-Sensitive Prostate Cancer: Multicenter Real-World Study

Abstract

Background: The management of metastatic hormone-sensitive prostate cancer (mHSPC) has evolved with the integration of androgen receptor signaling inhibitors (ARSIs) and metastasis-directed therapies (MDTs). Stereotactic body radiotherapy (SBRT) offers precise local control, yet real-world data on its combination with apalutamide remain limited. Methods: We conducted a multicenter retrospective cohort study including 134 patients with mHSPC treated with apalutamide and SBRT between February 2021 and December 2024. The primary endpoints were progression-free survival (PFS), local control (LC), and treatment safety. PSA kinetics and radiologic response were evaluated, and outcomes were analyzed according to PSA thresholds and treatment timing. Results: Most patients (93.3%) had low-volume disease; 97.1% presented with ≤5 metastases. At a median follow-up of 28 months, LC was 99.3% and 95.5% of patients were progression-free. Complete radiological response was achieved in 87.5% of patients, and 68.4% attained ultralow PSA levels (≤0.02 ng/mL). Undetectable PSA and radiologic complete response were independently associated with improved PFS (p = 0.010 and p = 0.011, respectively). Treatment was well tolerated, with grade ≥3 toxicity occurring in only 2.2% of patients. Conclusions: The combination of apalutamide and SBRT in mHSPC is associated with high local and systemic disease control and minimal toxicity in a real-world setting. This approach may delay systemic treatment intensification and the onset of castration resistance. Prospective studies are warranted to confirm these findings.