Biochemical Control and Toxicity Outcomes of SBRT vs LDR Brachytherapy in the Treatment of Low and Intermediate Risk Prostate Cancer
(2020, Full Text)
Low Dose Rate (LDR) brachytherapy and Stereotactic Body Radiation Therapy (SBRT) have both shown acceptable outcomes in the treatment of low and intermediate risk prostate cancer. Minimal data has been published directly comparing rates of biochemical control and toxicity with these two modalities.
We hypothesize that LDR and SBRT will provide similar rates of biochemical control, with LDR causing higher rates of acute GU toxicity and SBRT causing higher rates of chronic GI toxicity.Materials/Methods
All low and intermediate risk prostate cancer patients treated definitively with SBRT or LDR between 1/2010 and 12/2018 were captured. Patients with <1yr follow-up (FU) were excluded. Phoenix definition was used for biochemical failure and CTCAE v5.0 for toxicity grading. Independent t-tests were used to compare baseline characteristics, while repeated measure ANOVA was used to compare AUA, EPIC, and PSA scores between treatment arms over time. Biochemical control was estimated using the Kaplan Meier method. Differences in acute and late toxicity were assessed via Pearson chi-square.Results
470 and 125 patients were treated with LDR and SBRT. 219 LDR and 118 SBRT patients remained after exclusion. Median FU was 5.0yrs (interquartile range [IQR]:3.1-7.1) for LDR and 3.6yrs (IQR:3.0-4.7) for SBRT. All patients treated with LDR received 125Gy in a single fraction using Palladium-103 seeds. SBRT consisted of 42.5Gy in 5 fractions every other day. See Table for all patient characteristics, ADT use, risk groupings and median PSA values. Rate of 5yr biochemical control for LDR vs SBRT was 95.8% vs 97.5% (p = 0.585). There was no significant difference in PSA or AUA/EPIC questionnaires on repeated measure ANOVA over time, however LDR patients had higher mean AUA scores at one month (19.6 vs 11.4, p<.001) and 3 months (11.2 vs 9.6, p = 0.450). LDR had significantly lower grade 3 (G3) late GU (0% vs 3.3%, p = .007) and late GI toxicity (0% vs 3.3%, p = .007) rates. There were no acute G3+ or late G4+ toxicities.Conclusion
LDR and SBRT have both shown acceptable outcomes in the treatment of low and intermediate risk prostate cancer, but have not yet been directly compared. Our data shows similar biochemical control rates at 5 years with significantly higher late Grade 3 GU and GI toxicity in patients treated with SBRT. Further follow-up will be necessary to capture long-term control rates.