ESTRO 2020 Abstract Book

S1084 ESTRO 2020

Sunday 29 November

Session: Prostate outcome and dosimetry OC-1026 Toxicity and clinical outcomes of LDR versus HDR brachytherapy boost: propensity-score analysis A. Goni Ramirez 1 , A. Gomez-Iturriaga Piña 2 , M.B. De Paula Carranza 3 , E.M. Saenz de Urturi Albisu 3 , M. Egiguren Bastida 3 , M. Pagola Divasson 3 , I. Gutierrez Betondo 3 , N. Bultó Boque 3 , D.I. Ortiz de Urbina Ugarte 3 , V. Pastor Sanchis 4 , A. Bartrés Salido 4 , M. Erzilbengoa 4 , J. Rosa Nieto 3 1 fundacion Onkologikoa, Radiation Oncology, Donostia, Spain ; 2 Hospital Universitario Cruces, Radiation Oncology, Barakaldo, Spain ; 3 Fundación Onkologikoa, Radiation Oncology, Donostia, Spain ; 4 Fundación Onkologikoa, Medical Physics, Donostia, Spain Purpose or Objective To determinate and compare long-term biochemical control rates, survival and toxicity outcomes between brachytherapy-boost modalities (LDR versus HDR) in treatment of intermediate and high-risk prostate cancer patients. Material and Methods Between 2001 and 2016, 1136 patients with intermediate and high-risk prostate cancer were treated with external beam radiotherapy (EBRT) plus brachytherapy (BT) boost in our institution; 675 with permanent Iodine125 Low- Dose-Rate brachytherapy (LDR-BT) boost and 461 with temporal Iridium192 High-Dose-Rate brachytherapy (HDR- BT) boost. From those, 555 LDR-BT patients and 361 HDR- BT patients were selected for the execution of the propensity-score match, based on pre-treatment PSA, Gleason Score, clinical stage by MRI and duration of androgen deprivation therapy (ADT). Clinical outcomes and toxicity were evaluated and compared in these dose- escalation BT modalities. Toxicity was evaluated using Common Terminology Criteria for Adverse Events (CTCAE) version 4.0. Results A total of 408 paried (204 LDR-BT and 204 HDR-BT) patients were included in the final analysis after propensity-score matching. The median follow-up was 8 years for each cohort. Freedom from biochemical failure (FFBF) was 92.9% at 5 years and 81.5% at 10 years in LDR-BT group, and 91.6% and 85.9% at 5 and 10 years HDR-BT group, respectively. There was no difference in overall survival (OS) and prostate cancer specific survival (PCSS) at 10 years between modalities; 77,3% and 96.5% in LDR-BT group and 78.4% and 96% in HDR-BT group, respectively. Similarly, there was no statistical significant difference in metastases free survival at 10 years (92.1% in LDR-BT and 92.7% in HDR-BT). Six months after treatment, genitourinary (GU) grade 3 or higher toxicity was 2.9% in LDR-BT group and 2.0% in HDR-BT group, with no grade 3 or higher acute gastrointestinal (GI) toxicity in both groups. GU grade 3 or higher late toxicity was statistically unfavorable for LDR-BT: 19.1% and 24.5% at 5 and 10 years in LDR-BT group, and 13.7% and 15.7% at 5 and 10 years in HDR-BT group, respectively. No significant difference was found on gastrointestinal grade 3 or higher late toxicity: 4.9% at 5 years and 5.4% at 10 years in LDR-BT group and 2.5% for both 5 and 10 years in HDR-BT group.

Conclusion Although both LDR-BT and HDR-BT boost modalities achieve excellent long-term biochemical and survival rates in combination with EBRT for intermediate and high-risk prostate cancer, late grade 3 GU toxicity was statistically unfavorable for LDR-BT group. No differences in acute GU and GI toxicity were observed between LDR-BT and HDR- BT. Late grade 3 or higher GI toxicity was similar in both groups. OC-1027 Comparing GU toxicity of LDR I-125 prostate brachytherapy by robotic and manual loading techniques P. McLaughlin 1 , P.L. Nguyen 2 , I. Buzurovic 2 , D. Cail 2 , J. Adleman 2 , P.F. Orio III 2 , M.T. King 2 1 Centre de cancérologie du CISSS de l'Outaouais, Service de radio-oncologie, Gatineau, Canada ; 2 Dana- Farber/Brigham and Women's Cancer Center- Harvard Medical School, Department of Radiation Oncology, Boston, USA Purpose or Objective To examine genitourinary (GU) toxicity and biochemical outcomes after low-dose rate (LDR) prostate brachytherapy with day 30 MR/CT seed evaluation, and comparing robot-assisted implant by high dose rate- emulating LDR technique (HELP) and non-linked seeds with manually loaded, template-based real-time ultrasound- guided (MUS) implant with linked seeds. Material and Methods All patients diagnosed with prostate cancer from June 2008 - December 2016 receiving monotherapy or boost with iodine-125 at our institution were identified. Patient, disease and treatment information was compiled through chart review. A multivariable regression model was developed correlating a primary endpoint of IPSS recovery time to < 5 points of baseline to prostate D90, urethral V125, baseline IPSS, pre-treatment prostate volume by MRI or US monotherapy vs. boost, and HELP vs. MUS. Biochemical progression-free survival (bPFS) and worst acute and long term urinary CTCAE 5.0 toxicity (AUT and LUT: up to 12 months vs. 12+ months from implant) were also collected. Results A cohort of 436 consecutive patients with median follow- up of 39 months (IQR 25-65 months) was identified (4 excluded with missing data), 239 with HELP and 193 with MUS. Intent was monotherapy in 356 patients (145 Gy) and