ESTRO 2024 - Abstract Book

S2319

Clinical - Urology

ESTRO 2024

1 Azienda Ospedaliero-Universitaria Careggi, Radiation Oncology Unit, Florence, Italy. 2 University of Florence, Department of Biomedical, Experimental and Clinical Sciences "Mario Serio", Florence, Italy. 3 Institute for Cancer Research, Prevention and Clinical Network (ISPRO), Cancer Risk Factors and Lifestyle Epidemiology Unit, Florence, Italy. 4 Careggi University Hospital, Nuclear Medicine Division, Florence, Italy. 5 Azienda Ospedaliera Universitaria, Radiotherapy Unit, Parma, Italy. 6 Humanitas Clinical and Research Center, IRCSS, Radiotherapy and Radiosurgery Department, Milan-Rozzano, Italy. 7 IRCCS San Raffaele, Nuclear Medicine Department, Milan, Italy. 8 UC Davis, Department of Radiation Oncology, Davis, USA

Purpose/Objective:

Salvage radiotherapy (SRT) is one of the main treatment approaches after post-surgical biochemical relapse (BR) [1]. Recent guidelines recommend to perform PSMA PET/CT in patients with PSA > 0.2 ng/ml if results will influence treatment decisions, but little is known about the clinical impact of treatment options, especially in patients identified with oligometastases on PSMA PET/CT and no evidence of disease recurrence on conventional imaging. However, according to recent trials, next generation imaging (NGI) may significantly affect treatment in this setting [2]. Nonetheless, the best management in biochemically recurrent patients undergoing PSMA PET re-staging is debated, and prospective evidence is awaited. PSICHE (NCT05022914) is a prospective multicentric trial aimed to test a [68Ga]Ga- PSMA-11 PET/CT imaging tailored strategy. Here we present PSMA detection rate, treatment administered and early biochemical outcomes after enrolment completion.

Material/Methods:

[68Ga] Ga-PSMA-11 PET/CT imaging was performed in patients affected by BR after radical prostatectomy, defined as PSA>0.2 ng/ml. All patients with a PSA> 1 ng/ml were excluded from the trial. After imaging, a pre-defined treatment algorithm was proposed to all patients. SRT was proposed to all patients with a negative staging or positive imaging within prostate bed. Stereotactic body radiotherapy (SBRT) was used for all patients with pelvic nodal recurrence or oligometastatic disease. Androgen deprivation therapy (ADT)+/- androgen receptor targeted agent was provided in case of widespread metastatic disease. Observation was proposed in all patients in whom PSMA was negative and postoperative radiotherapy had already been performed. Stereotactic re-treatment of macroscopic relapse could be proposed in case of post SRT PSMA positive findings within prostate bed. Here we report early results focusing on rate of positive imaging and recurrence pattern, treatment administered (observation, SRT, SBRT or ADT), biochemical relapse free survival (BRFS), metastases free survival (MFS) and ADT free survival.

Results:

Analysis included 174 patients, with a median PSA at recurrence of 0.41 ng/ml (IQR 0.28-0.56). Overall, PSMA PET was found negative or positive within prostate bed in 121 patients (69.5%). Pelvic nodal disease or oligometastatic recurrence was found in 39 (22.4%) and 10 (5.7%) patients, respectively. Four patients (2.3%) were found to have polimetastatic disease. After staging, SRT, observation or re- treatment were proposed in 104 (59.7% ) (3 refused), 15 (8.6%) and 2 (1.1%) patients, respectively. All patients with pelvic nodal or oligometastatic disease underwent SBRT, administered in these setting in 39 (22.4%) and 10 (5.7%) patients. Upfront ADT was administered in 4 polimetastatic patients (2.3%). Following pre-defined treatment, CBR with PSA < 0.2 ng/ml after 3 months was reported in 78 patients (44.8%). Follow up >3 months was available for 159 patients. Further Biochemical relapse was detected in 50 patients (31.4%), with PSMA metastases detection in 27 cases (17%). ADT was prescribed in 13