PL04 Presentation Time: 2:15 PM

Purpose

To evaluate the necessity and/or dose of supplemental external beam radiotherapy (EBRT) in predicting biochemical failure (BF) and prostate cancer specific mortality (PCSM) in higher-risk prostate cancer patients implanted with Pd-103.

Materials and Methods

Eligibility criteria included clinically organ-confined disease with Gleason scores 7-9 and/or a pre-treatment prostate-specific antigen (PSA) of 10-20ng/mL. Trial 44/20 randomized 247 patients to 44Gy + 90Gy Pd-103 vs. 20Gy with 115Gy Pd-103. The subsequent 20/0 trial randomized 383 patients to the 20Gy arm vs. monotherapeutic 125Gy Pd-103. The brachytherapy prescription dose was prescribed to the prostate gland with generous periprostatic margins using extracapsular seeds and implantation of the proximal 10-12mm of the seminal vesicles. Post-implant computerized tomography (CT) based dosimetry was performed on day 0. Biochemical failure (BF) was defined as a PSA > 0.40ng/mL after nadir. Multiple clinical, pathologic and treatment parameters were evaluated for impact on BF, PCSM, and overall mortality(OM).

Results

For all 630 patients, the median follow up was 11.8 years with a day 0 D90 of 121.9% of prescription and a V100 of 98.3%. The 13-year BF, PCSM and OM were 5.8%, 1.0%, 30.4%, respectively. For the 44/20 patients (median follow up 13.7 years) BF, PCSM &OM were 8.9%, 2.4% and 39.7% while BF, PCSM & OM for 20/0 (median follow-up 10.4 years) were 3.6%, 0.0% and 21.5%. In part, the difference in outcome between the two groups was due to a significant difference in the number of accrued Gleason score (GS) 8-9 patients (15.8% versus 1.6%). BF and PCSM for FIR, UIR and HR were 3.5% and 0.0%, 7.5% and 1.9%, and 15.2%, and 4.3%, respectively. The median time to BF was 5.1 (range 0.7-10.7), 4.6 (range 0.7-12.3), & 2.9 (range 0.2-7.8) years for FIR, UIR & HR. Neither the addition of EBRT or dose impacted BF (Figure) or PCSM. In multivariate analysis, BF was most closely related to pre-implant PSA (p=0.019, HR=1.154), GS (p=0.008, HR=1.748) & percent positive biopsies (p=0.015, HR=1.020). PCSM was most closely related to pre-implant PSA (p= 0.02, HR=1.218) & GS (p< 0.001, HR=4.178). For all biochemically-controlled patients, the median PSA was< 0.02 ng/ml.

Conclusions

In this study, consistent, high-quality Pd-103 dose distributions with aggressive extra-capsular and proximal seminal vesicle coverage resulted in durable biochemical control rates in patients with higher-risk features. The addition of supplemental EBRT did not impact BF or PCSM.