ESTRO 2024 - Abstract Book

S2642

Clinical - Urology

ESTRO 2024

Purpose/Objective:

In localized prostate cancer, radical prostatectomy (RP) is a therapeutic option. Between 30-50% of these patients relapse at some point. Treatment with radiotherapy after surgery (PORT) with a high risk of relapse can be indicated both in adjuvant to surgery and in local rescue in case of biochemical or macroscopic progression, with similar oncological results. The growing interest in hypofractionated schemes on the prostate bed shows similar local control and toxicity rates as conventional fractionation. The main objective of this study is to analyze the oncological and toxicity results of the hypofractionated scheme in these patients.

Material/Methods:

Retrospective analysis of patients treated with intensity-modulated PORT (IMRT) on the bed after RP in a single center between January 2014 and September 2023. Histopathological variables, PSA kinetics, androgen deprivation treatment, progression and type, and treatment toxicity (CTCAE v.% scale) were reviewed.

Results:

A total of 198 patients treated with PORT were obtained. In 21 patients (10.6%) it was performed adjuvantly; in the remaining 177 (89.4%) it was indicated as salvage rescue due to evidence of local progression. The mean age at diagnosis was 62.78 years. The mean PSA at diagnosis was 16.5 ng/mL. Immediate PSA after surgery was 0.41 ng/mL. The mean highest PSA after PR was 1.81 ng/mL. 68 patients received ADT treatment (34.35%) before radiotherapy. The median time between surgery and radiotherapy was 55.7 months (4.58 years). The hypofractionation schemes used were: 54Gy/300 Gy in 141 patients (71.2%) without macroscopic recurrence by imaging and 60Gy/300 Gy in 57 patients (28.7%) with macroscopic recurrence confirmed by MRI or PET-CT. In 156 patients, PORT was performed exclusively on the bed (78.8%); 7 received PORT on the bed and lymph node chains (3.5%) and the remaining 35 received PORT on the bed + SABR on affected lymph nodes (17.6%).

The mean PSA at the first control after RT was 0.81 ng/mL. At the second control, it was 0.52 ng/mL, reaching a PSA NADIR of 0.22 ng/dl with a mean time to NADIR of 14.7 months.

With a mean follow-up of 57.3 months after PORT, 58 recurrences were observed (29.3%): 28 biochemical, 3 local, 3 local lymph nodes, 4 distant lymph nodes, 5 bone, 3 multiple distant lymph nodes, and 12 local and distant lymph nodes. Acute toxicity of some degree was observed in 103 patients (13 cases were G2 and 1 case was G3); 60 were genitourinary (GU), 13 were gastrointestinal (GI), and 30 both. No severe complications were observed.

Conclusion:

Hypofractionated schemes achieved good local control with very favorable results in terms of acute toxicity in our series. Better patient selection is needed in this scenario.