External Beam Radiotherapy With or Without Brachytherapy Boost in Men with Very High-Risk Prostate Cancer: A Large Multicenter International Consortium Analysis.

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International journal of radiation oncology, biology, physics


PURPOSE: Very high-risk (VHR) prostate cancer (PC) is an aggressive subgroup with high risk of distant disease progression, and systemic treatment intensification with abiraterone or docetaxel reduces PC-specific mortality (PCSM) and distant metastasis (DM) in men receiving external beam radiotherapy (EBRT) with androgen deprivation therapy (ADT). Whether prostate-directed treatment intensification with addition of brachytherapy (BT) boost to EBRT with ADT improves outcomes in this group is unclear.

METHODS AND MATERIALS: This cohort study from 16 centers across four countries included men with VHR PC treated with (i) dose-escalated EBRT with ≥ 24 months of ADT or (ii) EBRT+BT boost with ≥ 12 months of ADT. VHR was defined by National Comprehensive Cancer Network (NCCN) criteria (clinical T3b-4, primary Gleason pattern 5, or ≥ 2 NCCN high-risk features), and results were corroborated in a subgroup of men who met STAMPEDE trials inclusion criteria (≥ 2 of following: clinical T3-4, Gleason 8-10, or PSA ≥ 40 ng/mL). PCSM and DM between EBRT and EBRT+BT were compared using inverse probability of treatment weight-adjusted Fine-Gray competing risk regression.

RESULTS: Amongst the entire cohort, 270 underwent EBRT and 101 EBRT+BT. After a median follow-up of 7.8 years, 6.7% and 5.9% of men died of PC and 16.3% and 9.9% had DM after EBRT and EBRT+BT, respectively. There was no significant difference in PCSM (sHR, 1.47 [95% CI, 0.57-3.75]; P=.42) or DM (sHR, 0.72, [95% CI, 0.30-1.71]; P=.45) between EBRT+BT and EBRT. Results were similar within the STAMPEDE-defined VHR subgroup (PCSM: sHR, 1.67 [95% CI, 0.48-5.81]; P=.42; DM: sHR, 0.56 [95% CI, 0.15-2.04]; P=.38).

CONCLUSIONS: In this VHR PC cohort, no difference in clinically meaningful outcomes was observed between EBRT alone with ≥ 24 months of ADT compared with EBRT+BT with ≥12 months of ADT. Comparative analyses in men treated with intensified systemic therapy are warranted.





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