Genitourinary Cancer

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SU_31_2312 - Palladium-103 (Pd-103) prostate cancer brachytherapy: Long-term outcomes in over 700 patients

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Palladium-103 (Pd-103) prostate cancer brachytherapy: Long-term outcomes in over 700 patients
M. S. Peach, S. W. Dutta, K. Bauer-Nilsen, D. Campbell, B. Libby, and T. N. Showalter; Department of Radiation Oncology, University of Virginia, Charlottesville, VA

Purpose/Objective(s): To determine the long-term toxicity and disease outcomes after palladium-103 LDR brachytherapy for prostate cancer.

Materials/Methods: Retrospective analysis was performed on 706 consecutive patients treated with Pd-103 prostate brachytherapy from 1997 to 2016 at a single institution. Patient and treatment characteristics were collected including initial PSA, Gleason score (GS), T stage, risk group (per NCCN), monotherapy vs combined with external beam radiotherapy (EBRT) and androgen deprivation therapy (ADT). Disease and toxicity outcomes such as time to recurrence, time to metastases and acute/late gastrointestinal (GI), genitourinary (GU) and erectile dysfunction (ED) toxicities were also obtained. Post implant dosimetry was obtained from our treatment planning system database. Overall survival (OS), biological progression free survival (bPFS) and metastatic free survival (MFS) were calculated via Kaplan Meier estimate. Univariate (UVA) and multivariate analysis (MVA) models were used to determine disease and treatment factors that affect bPFS (by Phoenix criteria), MFS, OS, and toxicity rates.

Results: With a median follow-up of 133 months (range 1-234 months), n=460 and n=246 patients underwent PD-103 treatment as monotherapy or brachytherapy boost, respectively. Median monotherapy prescription dose was 125 Gy (range 100-125 Gy) and median LDR boost dose was 100 Gy (range 90-115 Gy). 306 patients (43.3%) received ADT with a median duration of 7 months (range 1-72 months). Most patients had low risk disease (46.7%) followed by intermediate (32.4%) and high-risk (20.8). Median OS was 230 months, with a 5-year OS of 95.6%, 10-year OS of 84.3% and 15-year OS of 70.7%. The bPFS at 5, 10 and 15 years was 93.5%, 88.1%, 84.9%, respectively, and MFS at 5, 10, and 15 years was 98.1%, 95.9%, and 94.8 %, respectively. On MVA, bPFS, MFS, and OS was worsened with T3 and GS ³ 8 disease (p < 0.05) and not influenced by EBRT or ADT (p > 0.05). bPFS was improved with higher D90% (p = 0.033). Grade 3 GU and GI toxicities were seen in 21 patients (3.4%) and 1 patient (0.2%) respectively, with no grade 4 events. At last follow up 56% of previously potent patients had developed ED. On MVA, late grade ³ 2 GI toxicity was higher with more rectal volume receiving 100% prescription dose (V100, HR 4.379 per cc, p < 0.001). On UVA, late grade ³ 2 GU toxicity was higher with more prostate volume receiving 200% prescription dose (HR 1.03 per cc, p=0.012).

Conclusion: The present work is the largest reported series of Pd-103 prostate brachytherapy to date, confirming the isotope and technique as a long-term, effective treatment with greater than 10-year median follow-up. Dosimetric predictors for disease control and late GI toxicity are consistent with the literature on iodine-125 brachytherapy outcomes.

Author Disclosure: M.S. Peach: None. K. Bauer-Nilsen: None. D. Campbell: None. B. Libby: None. T.N. Showalter: None.

Matthew Peach, MD, PhD

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