ASCO GU 2019: Enzalutamide and ADT with Salvage Radiation in Men with High-Risk PSA Recurrent Prostate Cancer: The STREAM trial

San Francisco, CA (UroToday.com) Standard of care therapy for men with biochemical recurrence of radical prostatectomy is salvage external beam radiotherapy (EBRT) followed by androgen deprivation therapy (ADT)1. Unfortunately, 51% of men may have PSA recurrence at 2 years, even after salvage EBRT and docetaxel based chemotherapy2. This phase II study evaluates the addition of enzalutamide to standard of care EBRT + ADT. 


Summary:

Patients with PSA relapse within 4 years of radical prostatectomy with a Gleason of 7-10 and PSA between 0.2 and 4.0 and rising were included. Patients must have had no metastases by standard CT/bone scan and node positive men were eligible if they had less than 3 prior positive nodes which had been resected. All patients were given enzalutamide at the standard dose of 160 mg/day as well as ADT for 2 months, which was then followed by EBRT (64.8-68 Gy) for 6-8 weeks. ADT and enzalutamide were continued during this period of time for a total of 4 additional months for a total of 6 months of ADT and enzalutamide. The primary objective was to determine the 2 year progression free survival of men who have had testosterone recovery to >100. 
In terms of baseline characteristics, the median age was 64. The majority of patients were white (90%), and 47% had a Gleason score of 8-10. 21% had prior nodal disease at radical prostatectomy and the median time since radical prostatectomy was 1.1 months. 

After a median follow up of 29.5 months, the median progression free survival for patients with testosterone recovery was 64.9%. 69% of patients in the entire cohort continue to have undetectable PSA at 2 years. 8 patients had node positive disease at prostatectomy and the 24 month and 36 month progression free survival was 25%. Testosterone recovery occurred in 95% of patients. 

(Percentage of patients experiencing clinically meaningful deterioration)

In terms of quality of life, a significant number of patients experienced short term reductions in quality of life with respect to urinary irritative score, urinary incontinence score, bowel score, sexual score, and hormonal score. However, most men experience recovery by 12-24 months.


Conclusion:

Salvage therapy with combination ADT plus enzalutamide for 6 months with salvage EBRT is safe with encouraging efficacy data in this small phase II study of men with PSA recurrent prostate cancer after radical prostatectomy. Quality of life initially diminishes with treatment but most patients recover within 12 to 24 months. This study‚Äôs primary endpoint of PFS at 2 years was 65% which compares favorably to historical controls and warrants further study in a randomized phase III clinical trial for this high risk population of patients where treatment is with curative intent.  

References:
1. Shipley WU, Seiferheld W, Lukka HR, et al. Radiation with or without Antiandrogen Therapy in Recurrent Prostate Cancer. 2017;376:417-28.

2. Armstrong AJ, Halabi S, Healy P, et al. A phase 2 multimodality trial of docetaxel/prednisone with sunitinib followed by salvage radiation therapy in men with PSA recurrent prostate cancer after radical prostatectomy. Prostate Cancer And Prostatic Diseases 2016;19:100.

Presented by: Andrew Armstrong, MD

Written By: Jason Zhu, MD. Fellow, Division of Hematology and Oncology, Duke University, Twitter: @TheRealJasonZhu at the 2019 American Society of Clinical Oncology Genitourinary Cancers Symposium, (ASCO GU) #GU19, February 14-16, 2019 - San Francisco, CA

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