ESTRO 2021 Abstract Book

S1135

ESTRO 2021

Salvage treatment consisted of volumetric modulated arc salvage radiotherapy (SRT) based on multiparametric MRI with or without neoadjuvant androgen-deprivation therapy (ADT, LHRH agonist). The whole gland was treated and a whole pelvis irradiation was performed when the Roach formula was > 15%. Outcome was measured as cancer-specific survival (CSS) and biochemical progression free-survival (bPFS). The latter was defined according to the ASTRO Phoenix definition (PSA nadir + 2ng/ml). The genitourinary (GU) and gastrointestinal (GI) toxicities were evaluated using The CTCAE v4.0. Results Overall, 11 patients (14%) had a local relapse, of whom 7 (64%) were diagnosed by biopsy and 4 (36%) by 68 Ga- PSMA PET-CT. Median pre-SRT PSA was 7.5 ng/ml (IQR: 4.9 - 11). Median time between HIFU and SRT was 25 months (interquartile range [IQR]: 16-32). All patients received at least 74 Gy (IQR: 74 – 77; median 77) combined with ADT in 72% of the cases. Six patients (55%) received a whole pelvis irradiation of 56 Gy (IQR: 48.5 - 56) in 35 fractions (IQR: 26 - 35). Duration of the ADT was 18 months (62%) or 6 months (38%). With a median follow-up of 16 months (IQR: 9 - 19), CSS and bPFS are 100%. Eight patients (73%) experienced Grade 1 GU symptoms, four patients (36%) had Grade 1 GI and one patient (9%) had Grade 2 GI. No toxicity (Grade >2) was reported. Conclusion Salvage radiotherapy after HIFU seems to be efficient and safe. Prospective studies and longer follow-up are needed to confirm these findings. PO-1385 PSA bounce and biochemical failure analysis in low dose rate iodine-125 prostate brachytherapy boost N. Bultó Boqué 1 , A. Goñi Ramírez 1 , B. de Paula Carranza 1 , E.M. Sáenz de Urturi Albisu 1 , M. Pagola Divasson 1 , D.I. Ortiz de Urbina Ugarte 1 , J. Rosa Nieto 1 , A. Ayete Andreu 1 , M. Erzilbengoa Izaguirre 2 , V. Pastor Sanchís 2 , A. Bartrés Salido 2 , N. Suárez Álvarez 2 1 Onkologikoa UGC Onco-Hematologia Gipuzkoa, Radiation Oncology, San Sebastián, Spain; 2 Onkologikoa UGC Onco-Hematologia Gipuzkoa , Medical Physics, San Sebastián, Spain Purpose or Objective To describe the incidence, timing, and magnitude of the benign prostate-specific antigen (PSA) bounce after external beam radiotherapy (EBR) and low-dose-rate iodine-125 brachytherapy (LDR-BT) boost, its correlation with biochemical, clinical and/or dosimetric factors and the possible association between PSA bounce and From 2001 to 2015, 668 men with intermediate and high risk prostate cancer were treated with a combination of EBRT (46 Gy) and LDR-BT boost (108 Gy) with or without androgen deprivation therapy (ADT) in our institution. Of the 668 initial patients, 516 that had a PSA follow-up ≥ 60 months with PSA checked at least every 6 months were included for the analysis. An analysis of the subgroup of patients without ADT was performed. All patients received EBRT 46 Gy in 23 fractions of prostate irradiation and preplanned stranded- seed I-125 implant. PSA bounce was defined as an increase of ≥ 0.2 ng/ml with spontaneous return to prebounce level or lower without any intervention. BF was defined following the Phoenix criteria as PSA nadir + 2 ng/ml without any spontaneous decrease. Results The median follow-up was 122 months (60-231 months). Stratified by risk, 289 (58.9%) patients had intermediate risk and 227 (41.1%), high risk of progression. Patients that received ADT were 286 (55.4%). PSA bounce was found in 81 (15.7%) men. Median prebounce PSA was 0.75 ng/ml (0.01-2.80 ng/ml) and median height of PSA bounce was 1.63 ng/ml (0.21-7.34 ng/ml). Median duration of PSA bounce was 17 months (6-47 months) and 40.7% of PSA bounce had a magnitude >2 ng/ml. BF was seen in 64 (12.4%) patients of whom 3 had a PSA bounce. Median time to PSA bounce was 17 months (3-73 months) whereas median time to BF was 73 months (14-186 months). Among 81 patients with a PSA bounce, 76 (93.8%) presented it before 40 months while, among 64 patients with BF, 61 (95.3%) presented it after 40 months. In the multivariate analysis, the younger age (<65 years) and the absence of ADT were predictor factors of PSA bounce. Progression Free Survival (PFS) at 5, 10 and 15 years were 99%, 96% and 96% in patients that present PSA bounce and 93%, 85% and 79% among patients without it (p 0.003). When we analyzed the subgroup of patients not treated with ADT (230 patients), 65 (28.3%) presented PSA bounce and the BF was seen in 32 (13.9%) men. Age (<65 years) was the only predictor factor in the multivariate analysis in this subgroup. PFS at 5, 10 and 15 years in this subgroup were 98%, 95% and 95% among the patients with PSA bounce and 91%, 82% and 74% among the ones without it (p 0.008). Biochemical Failure (BF). Materials and Methods