ESTRO meets Asia 2024 - Abstract Book

S59

Interdisciplinary – Brachytherapy

ESTRO meets Asia 2024

Alai Goñi Ramirez 1 , Mikel Larruskain 2 , Macarena Sevilla 2 , Darya Chyzhyk 2 , Maider Alberich 2 , Mikel Egiguren 1 , Vicent Pastor 3 , Albert Bartrés 1 , Eva María Saénz de Urturi 1 , Daniel Alberto Roura 1 , Ane Mugika 1 , María Pagola 1 , Leyre Gonzalez 1 , Sara Palacios 1 , Usoa Iceta 1 , Nuria Bultó 1 , Amaia Sanchez 1 , Julian Minguez 1 , Intza Uranga 1 , Ane Dehesa 1 , Ane Otaegui 1 , Xabier Gurutzeaga 1 , Beraldo Martinez 1 , Jose María Urraca 1 , Arrate Querejeta 1 1 Radiation Oncology, Onkologikoa - UGC Oncología Gipuzkoa, San Sebastián, Spain. 2 Data Science, NARU Intelligence, San Sebastian, Spain. 3 Medical Physics, Onkologikoa - UGC Oncología Gipuzkoa, San Sebastián, Spain

Purpose/Objective:

The aim of this study is to evaluate biochemical, survival and toxicity long-term outcomes of patients with high risk prostate cancer treated with high-dose-rate brachytherapy (HDR-BT) boost in combination with external beam radiation therapy (EBRT) during 20 years in a single institution.

Material/Methods:

Between October 2004 and December 2016, 378 patients with high-risk prostate cancer were treated with CT image guided HDR-BT boost and EBRT combination schema. Until November 2009, 205 patients treated (54.23%) received 46Gy EBRT followed by a two-fraction administration of 9, 9.5 or 10Gy HDR-BT boost in a single implant. From November 2009, 173 patients were treated with single fraction 15Gy HDR-BT boost followed by 46Gy EBRT. Patients with less than 2-year follow-up post treatment were excluded from the study. Kaplan-Meier method was used to study both all population and population stratified by number of delivered fractions Biochemical-recurrence free survival (BFS), metastasis-free survival (MFS) and cancer specific free survival (CSFS). Pairwise log-rank tests were used to determine significant differences. Cox proportional hazards regression was used to assess the influence of prognostic factors on BFS and CSFS. The median follow-up was of 130.12 months. Median age was 70.22 (Q1 64.8; Q3 74.3), median PSA value in diagnosis was 11.32 (Q1 7, Q3 20) and 92.33% of patients received androgen deprivation therapy (ADT). The most frequent tumor stages were T3a (153, 40.32%), T2c (84, 22.28%) and T3b (61, 16.18%). Most patients had a Gleason score equal to 7 (48.54%) and 20.69% of patients had a Gleason score > 7. Population CSFS was 99.4% (95% CI 97.8 – 99.9) at 5 years, 95.4% (95% CI 92.3 – 97.3) at 10 years, 91% (95% CI 84.9 – 94.7) at 15 years and 91% (95% CI 84.9 – 94.7) at 20 years. BFS and Metastasis Free Survival MFS were 90.9% and 96.2% at 5 years, 81.4% and 91.5% at 10 years, 74.6% and 83.9% at 15 years and 72.8% and 81.9% at 20 years, respectively. Single fraction vs 2 fraction regimens were compared during a 10-year follow-up time. Ten-year BFS, MFS and CSFS single fraction versus 2 fractions were 79.6% vs 82.6% (p = 0.784), 90.5% vs 91.6% (p = 0.8385) and 95.3% vs 95.4% (p = 0.99), respectively. Ten-year Genitourinary Toxicities Free Survival (GUTFS) and Gastrointestinal Toxicities Free Survival (GITFS) were compared by fraction regime. Single fraction versus 2 fractions results were 89.7% vs 82.2% (p = 0.07) and 99.4% vs 98.3% (p = 0.44) for GUTFS and GITFS respectively. On Cox regression model for 20-years BFS, PSA in diagnosis (p < 0.001), Gleason score > 7 (p = 0.001) and T3b tumor stage (p = 0.006) were significantly associated with increased hazard. For 20-years CSFS, PSA in diagnosis (p < 0.001) and Gleason score > 7 (p = 0.022) had a significant effect on increased hazard. Higher PSA value in Results: