ESTRO 2024 - Abstract Book

S2353

Clinical - Urology

ESTRO 2024

Pieve Emanuele, Italy. 4 IRCCS Humanitas Research Hospital, Radiotherapy and Radiosurgery Department, Rozzano, Italy. 5 Fondazione IRCCS San Gerardo dei Tintori, Department of Medical Physics, Monza, Italy. 6 ASST Papa Giovanni XXIII, Department of Radiation Oncology, Bergamo, Italy. 7 ASST Papa Giovanni XXIII, Department of Medical Physics, Bergamo, Italy. 8 AULSS 1 Dolomiti, Department of Radiation Oncology, Belluno, Italy

Purpose/Objective:

Postoperative radiotherapy (RT) is known to enhance overall and progression-free survival, whether as an adjuvant or early salvage treatment. However, traditional RT regimens are often lengthy, costly, and burdensome for patients. Stereotactic Body Radiation Therapy (SBRT) could offer similar benefits while reducing treatment duration and costs, making it more accessible and convenient for patients.

Here, we report the updated results of POPART trial (NCT04831970), investigating the feasibility of postoperative SBRT for prostate cancer in terms of toxicity and quality of life (QoL).

Material/Methods:

The POPART trial is a multicentric prospective observational trial that assessed the feasibility of postoperative SBRT for prostate cancer. Patients with PSA levels ≥0.1– 2.0 ng/mL after radical prostatectomy (RP) and no distant metastases, underwent linac-based SBRT, delivered with Volumetric Modulated Arc Therapy (VMAT) in five fractions every other day for a total dose of 32.5 Gy (EQD21.5 =74.3 Gy) to the prostate bed, delineated according to the GFRU guideline. Late toxicity was assessed using CTCAE v.5 scale; while patient-reported outcomes and biochemical control were evaluated through EPIC-CP, ICIQ-SF, IIEF 5 questionnaires and PSA serum levels, respectively. Paired t-test was used to compare pre-treatment and post-treatment questionnaire scores, with minimally important differences (MID) established as a change in the questionnaire scores of > 0.5 pooled standard deviation (SD) from the baseline. A logistic regression analysis was performed to evaluate potential associations between specific patient-related, tumour-related or treatment-related factors and a worsening of clinical outcomes.

Results:

From April 2021 to April 2023 a total of 50 pts were enrolled and treated, with a median age of 70 (52-83) years. Median follow-up was 12.2 (3-27) months. Table 1 displays their baseline demographic and clinical characteristics, along with treatment details. Median PSA level before RT was 0.3 (0.1-1.9) ng/mL. Baseline assessments revealed that 21 patients already had sexual dysfunction. The median CTV and PTV were 25.4 cc and 62.5 cc, respectively.

No late severe (≥G2) gastrointestinal (GI) or genitourinary (GU) toxicity was observed during the study. Late G1 urinary and bowel toxicity occurred in 46% and 4% of patients, respectively.

Median post-treatment PSA nadir was 0.04 (0.00-0.84) ng/mL. Six patients experienced biochemical failure, including two patients with nodal relapse treated with SBRT.

According to EPIC-CP and ICIQ-SF questionnaires, four patients (8%) had a decline in urinary continence at the last follow-up. In the urinary irritation/obstruction domain of the EPIC-CP questionnaire, a MID was noted in 4% of patients, while no MIDs were detected in the bowel function and hormonal symptom domains. When considering