Abstract:

Objective: To compare radical prostatectomy (RP) versus permanent prostate brachytherapy (PPB) as primary local treatment modalities in delaying disease progression to castration-resistant prostate cancer (CRPC) among patients with oligometastatic prostate cancer (omPCa) receiving standard androgen deprivation therapy (ADT), and to provide clinical evidence for individualized treatment strategies. Methods: We performed a retrospective cohort analysis of 88 patients diagnosed with omPCa (defined as ≤5 metastatic lesions) at a single tertiary center between April 2011 and August 2019. All the patients, after receiving either RP (n=62) or PPB (n=26), were placed on a regimen of continuous ADT. To address significant baseline disparities-notably in patient age, presenting prostate-specific antigen (PSA) levels, and nodal disease burden: A 1 ∶ 1 propensity score matching (PSM) protocol was implemented. Matching variables included age at diagnosis, baseline PSA, clinical T stage (≤T2c vs. ≥ T3), and nodal status (N0 vs. N1). The primary study endpoint was the time interval from ADT initiation to CRPC development, as defined by the prostate cancer working group 3 (PCWG3) criteria. Survival outcomes were compared using Kaplan-Meier curves and the Log-rank test. Independent risk factors for progression were identified through both univariate and multivariate Cox proportional hazards regression analyses. Results: Prior to PSM, the RP and PPB groups exhibited significant differences in key prognostic factors: the PPB group was older (mean 73.2 vs. 68.1 years, P=0.002), had a higher median PSA (31.2 vs. 9.8 μg/L, P=0.002), and had a greater incidence of lymph node involvement (42.3% vs. 12.9%, P=0.006). Following PSM, a balanced cohort of 36 patients (18 in each group) was achieved. Over a median follow-up of 30.5 months (range: 3.2 to 113.4 months), 15 patients (17.0%) developed CRPC, with 8 events occurring in the PPB group and 7 in the RP group. Survival analysis demonstrated a consistent, statistically significant advantage for RP. In the pre-matched cohort, the RP group showed a significantly delayed progression to CRPC (Log-rank P=0.033, HR=3.38, 95%CI: 1.10-10.40), with a median CRPC-free survival of 80.0 months for PPB and not reached for RP. In the matched cohort, the survival advantage of RP was more pronounced (Log-rank P=0.032, HR=4.60, 95%CI: 1.14-18.49), with a median CRPC-free survival of 80.0 months for PPB and not reached for RP. Multivariate Cox regression, adjusting for T and N stages, confirmed treatment modality as a powerful independent predictor. Patients treated with PPB faced an 8.56-fold higher risk of progression compared with those treated with RP (HR=8.56, 95%CI: 1.51-48.64, P=0.015). Advanced primary tumor stage (≥T3) was also identified as a significant independent risk factor (HR=10.29, 95%CI: 1.75-60.57, P=0.010). Conclusion: For patients with omPCa receiving ADT, the choice of local therapeutic intervention significantly impacts the time to CRPC. Radical prostatectomy is associated with a markedly longer delay in disease progression to the castration-resistant state compared with permanent prostate brachytherapy, with the treatment modality itself serving as a strong independent prognostic factor. These findings underscore the importance of considering the type of local therapy in the multimodal management of omPCa and provide a rationale for individualized treatment planning. Prospective, randomized trials are necessary to validate these observations and further define optimal therapeutic paradigms.

Key words: Oligometastatic prostate cancer, Radical prostatectomy, Permanent prostate brachytherapy, Castration-resistant prostate cancer, Propensity score matching