Trends in Primary- and Metastasis-Directed Radiotherapy Uptake and Survival in Metastatic Prostate Cancer.

Background/Objectives: This study investigates trends in radiotherapy utilization in men with metastatic prostate cancer, particularly in response to pivotal trials like STAMPEDE and STOMP, which demonstrated survival benefits for primary- and metastasis-directed radiotherapy. Methods: Using data from the National Cancer Database, the study analyses changes in treatment patterns post-2018. Results: Prior to 2018, 13.3% and 10.9% of patients with metastatic prostate cancer received primary- and metastasis-directed radiotherapy, respectively; these proportions increased modestly to 14.0% and 12.1% following 2018 (χ2p < 0.0001 for both). Significant differences in comorbidity prevalence were observed both temporally (CDCI mean 0.35 prior to 2018 vs. 0.46 post-2018, p < 0.0001), and between those treated with primary- and metastasis-directed radiotherapy (CDCI mean 0.34 in primary-directed vs. 0.45 in metastasis-directed, p < 0.0001). Primary-directed radiotherapy was associated with improved overall survival across all years (HR 0.87, p < 0.0001), but it was associated with lower survival when restricted to post-2018 diagnoses (HR 1.24, p < 0.0001). Metastasis-directed radiotherapy was not significantly associated with overall survival benefit regardless of era (M1a: HR 1.58, p = 0.27; M1b: HR 0.97, p = 0.29), though non-receipt after 2018 was associated with markedly increased mortality (HR 18.54, p < 0.0001). Conclusions: Pivotal clinical trials temporally align with shifts in radiotherapy practices among M1 disease subgroups. The potential survival benefit of radiotherapy to the primary site and to metastases among patients with metastatic disease merits further investigation in the real-world setting. Further work may highlight differences in patient populations or overall efficacy of radiotherapy in these populations.