ESTRO 2023 - Abstract Book

S1176

Digital Posters

ESTRO 2023

To investigate the feasibility of ultrahypofractionated radiotherapy to prostate bed in patients with biochemical and/or clinical relapse following radical prostatectomy enrolled in the prospective observational multicentric POPART trial (NCT04831970). Materials and Methods Patients with post-radical prostatectomy PSA level of ≥ 0.1-2.0 ng/mL or local relapse at PSMA PET CT or multiparametric MRI were treated with Linac-based Volumetric Modulated Arc Therapy (VMAT) on prostate bed up to a total dose of 32.5 Gy in five fractions every other day (EQD21.5 = 74.2 Gy). Androgen deprivation therapy (ADT) was allowed at physician’s discretion. Maximum acute toxicity was assessed with Common Terminology Criteria for Adverse Events version 5 (CTCAE_v5) scale. In addition, International Consultation on Incontinence Questionnaire-Short Form (ICIQ-SF) score was used at baseline and during the follow-up. Results From April 2021 to June 2022 thirty men with a median age of 72 years (range 55-82) were enrolled in three Italian centres. The majority of them (74%) had a biochemical relapse only, while 8 patients (26%) had a local relapse. Median time from prostatectomy was 54.5 months (range 7-155). Median PSA level before RT was 0.30 ng/ml (range 0.18-1.89 ng/ml). Four patients (13%) received ADT. At baseline median ICIQ-SF score was 1 (range 0-8). The median PTV was 72 cc (range 14.8 250.2 cc). No treatment interruptions were registered. After SBRT completion only one instance of Grade 2 acute gastrointestinal (GI) toxicity was documented; no ≥ Grade 2 acute genitourinary (GU) toxicity was observed, and 3 patients experienced Grade 1 GU side effects. At three months follow-up no GI and ≥ 2 GU side effects were reported; Grade 1 GU toxicity was detected in 3 patients (10%). No changes in ICIQ-SF were assessed. Three months after SBRT all but two patients, who progressed distantly, were found biochemically controlled with a median post-treatment PSA level of 0.07 ng/ml (range 0-0.48 ng/ml). Conclusion Post-prostatectomy ablative radiation therapy for biochemical and/or clinical relapse allowed a convenient and safe treatment with negligible early side effects, showing that high focused radiation in few fractions to the prostate bed with robust conformality and modulation, abrupt dose fall off and image guidance can be extended to the postoperative setting. Long term results are needed to confirm these findings. 1 N.N. Petrov National Cancer Center, Radiotherapy, St Petersburg, Russian Federation; 2 N.N. Petrov National Cancer Center, Urology, St Petersburg, Russian Federation; 3 N.N. Petrov National Cancer Center, Chemotherapy, St Petersburg, Russian Federation; 4 N.N. Petrov National Cancer Center, Radioterapy, St Petersburg, Russian Federation Purpose or Objective to compare biochemical recurrence free survival (BRFS) and toxicity outcomes of modern combined treatments of high, very high-risk prostate cancer (HRVHRPC): antiandrogen deprivation (AD) with radiotherapy (RT) and AD with surgery. Materials and Methods two prospective observational single center studies of RT and surgical treatment of HRVHRPC patients were included in the analysis. In 149 patients, we compared whole pelvic RT (45-50Gy) with high dose rate brachytherapy (15Gy) or stereotactic (3x7Gy) boost to the prostate. Prospective surgical study compared neoadjuvant chemotherapy-AD with adjuvant AD in 139 HRVHRPC patients treated by prostatectomy and extended lymph node dissection. Results In 149 patients that received RT with AD (12-24 months) 3- and 5-year BRFS were 74.6-76.5% and 66.8-67.7%. Late grade III genitourinary toxicity was mentioned in 1 men (brachytherapy boost) and late grade III-IV rectal toxicity in 3 patients (2%) (all with stereotactic boost). 5 year BRFS was significantly lower in surgical groups: 35.7-44.2%. Late grade III incontinence detected in 14-18%, abscess in 1 and neuropathy of obturator nerve in another 1 patient. Conclusion In high, very high-risk prostate cancer whole pelvic RT with brachy/stereotactic boost and AD associated with significantly higher 5-year BRFS than prostatectomy with extended lymph node dissection and AD or chemotherapy-AD. PO-1453 A comparison between surgical and radiotherapeutic treatment of high-very high-risk prostate cancer. S. Novikov 1 , A. Nosov 2 , R. Novikov 1 , N. Buevitch 3 , E. Samarceva 1 , Y. Merejko 1 , S. Protcenko 3 , S. Kanaev 4

PO-1454 SBRT for prostate cancer with or without Elective Nodal Irradiation

J. Canales 1 , T. Merino 1 , P. Reyes 1

1 Pontificia Universidad Católica de Chile, Hemato-oncology, Santiago, Chile

Purpose or Objective Feasibility to randomize and assess acute toxicity of patients with unfavorable intermediate-risk and high-risk to prostate and seminal vesicle with or without Elective Nodal Irradiation (ENI) with SBRT in Academic Center in Latin America. In addition, evaluate the fidelity of the treatment protocol and the dose restriction to the organ at risk (OAR).