S1273
Clinical - Urology
ESTRO 2026
treated between 2010–2024 across eight centres. Patients receiving prostate ± nodal RT with RT to all metastases and systemic therapy were classified as ART (n=150), those receiving systemic therapy alone or incomplete RT comprised the NPRT group (n=67). To minimize confounding, propensity score matching (PSM) was performed using a probit model including age, ECOG status, PSA, T/N stage, ISUP grade, number of metastases, and type of systemic therapy. One-to- one nearest-neighbour matching without replacement yielded 67 matched pairs (mean standardized bias reduced from 38% to 18%). Survival outcomes were estimated with Kaplan–Meier and Cox models. Results: At a median follow-up of 39 months, ART was associated with longer time to castration resistance (p=0.004) and time to subsequent systemic therapy (p=0.006), ), while a trend toward inferior OS was observed (median 84 vs 129 months, p=0.08). After PSM, OS difference became significant (log-rank p=0.03, Cox HR=2.97, 95% CI 1.18–7.49, p=0.02). Treatment type (ART vs NPRT) remained the only predictor of OS (p=0.02). Despite covariate adjustment, residual confounding remained evident. In the NPRT group, patients had more distant metastases and higher ISUP grade (p=0.02 and p=0.002, respectively).Figure 1. Overall survival in propensity score-matched cohort.
Conclusion: In this largest real-world cohort of synchronous omPC, comprehensive local therapy was associated with inferior overall survival after propensity score adjustment. Although matching improved baseline balance, residual confounding persisted, as the NPRT group had higher metastatic burden and higher ISUP grades, yet demonstrated better OS. These findings should be interpreted with caution, as the survival difference might reflect selection bias, differences in systemic therapy, or unmeasured factors rather than a true detrimental effect of radiotherapy. Potential late or subclinical toxicities from large-field irradiation may also have influenced the observed outcomes. Prospective randomized trials are needed to clarify the optimal integration of local and systemic therapies and to refine patient selection in synchronous oligometastatic prostate cancer. References: 1.Aizawa R, Takayama K, Nakamura K, et al. Long - term clinical outcomes of external beam radiation therapy for oligometastatic prostate cancer: A combination of prostate - targeted treatment and metastasis - directed therapy. Int J Urol. 2021 July;28(7):749–55. 2.Hao C, Ladbury C, Lyou Y, et al. Long-Term Outcomes of Patients on a Phase II Prospective Trial of Oligometastatic Hormone-Sensitive Prostate Cancer Treated With Androgen Deprivation and External Beam Radiation. Int J Radiat Oncol. 2022 Nov;114(4):705–10. 3.Imber BS, Varghese M, Goldman DA, et al. Clinical Outcomes of Combined Prostate- and Metastasis-Directed Radiation Therapy for the Treatment of De Novo Oligometastatic Prostate Cancer. Adv Radiat Oncol. 2020 Nov;5(6):1213–24. Keywords: oligometastatic, prostate cancer, MDT
Table 1. Baseline characteristics of patients after PSM.
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