PV QA 1 - Poster Viewing Q&A 1
SU_24_2248 - Dose-Escalated Stereotactic Body Radiation Improves Outcomes in Patients with Low- and Intermediate-Risk Prostate Cancer
Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3
Dose-Escalated Stereotactic Body Radiation Improves Outcomes in Patients with Low- and Intermediate-Risk Prostate Cancer
B. W. Cox1, Z. Rana2, L. Lee3, and L. Potters1; 1Zucker School of Medicine at Hofstra/Northwell, Hempstead, NY, 2Northwell Health, Lake Success, NY, 3Department of Radiation Medicine, Zucker School of Medicine at Hofstra/Northwell, Northwell Health, Lake Success, NY
Purpose/Objective(s): Long term data for stereotactic body radiotherapy (SBRT) for the treatment of prostate cancer (CaP) beyond 5 years suggest that the standard dose of 36.25 Gy in 5 fractions utilizing) may be associated with higher PSA recurrence. It is therefore reasonable to consider a growing rationale for higher doses to improve outcomes. This study presents a prospective phase I/II, IRB approved dose-escalated SBRT trial and assessed the impact of dose level on outcomes, quality of life, and toxicity.
Materials/Methods: From 2011 to 2016, 26 patients (pts.) with low and intermediate-risk CaP received 40, 45, and 50 Gy in five fractions to the prostate and seminal vesicles in cohorts of 9, 10, and 7 pts. Self-reported QOL was prospectively measured from the Expanded Prostate Cancer Index Composite (EPIC) and International Prostate Symptom Score (IPSS) at baseline and intervals of every 3 months for the first two years followed by every 6 months thereafter. Common Toxicity Criteria for Adverse Events v. 4.03 data was collected to observe acute and late toxicities. No pts. received androgen deprivation therapy.
Results: Median follow-up was 4.8 years. PSA nadir was 0.9, 0.39, and 0.33 ng/ml, in the 40, 45, and 50 Gy cohorts, respectively. There was a significant difference in PSA nadir comparing the 40Gy to the 45 and 50Gy cohort (p < 0.02). A PSA nadir < 0.5 ng/ml was seen in 22%, 80%, and 71% of patients receiving 40, 45, and 50 Gy, and < 0.2 ng/ml in 11%, 50%, and 71% of patients after 3 years. After 5 years, a PSA nadir < 0.5 ng/ml was achieved in 100% of patients receiving 45 Gy and 50Gy compared to 33% receiving 40 Gy. There was an increase in EPIC and IPSS scores followed by a return to baseline over two years for all cohorts. Acute Grade 2 urinary toxicity occurred in 10 pts. with no significant difference among treatment arms. The three pts. experiencing late Grade 2 toxicity were in the 45 or 50 Gy cohort. There were no Grade 3 or higher toxicities. On univariate analysis Grade 2 toxicity was only significantly associated with prostate size >60 cc (p < .01). One biochemical failure was observed in the 40 Gy arm after 3.6 years resulting in a freedom from biochemical failure rate of 96% at 5-years. Prostate cancer specific survival was 100% and actuarial overall survival was 96%.
Conclusion: This prospective dose-escalation study identified acceptable GU and GI toxicity for each dose level, including 50Gy. We also demonstrated that higher doses of 45 and 50 Gy are associated with improved PSA nadir. Further follow-up is needed to assess PSA freedom from recurrence and late toxicity.
Author Disclosure: B.W. Cox: Employee; NYU. Z. Rana: None. L. Lee: None. L. Potters: None.