ESTRO 2024 - Abstract Book

S2298

Clinical - Urology

ESTRO 2024

missing stratification variables were excluded. Subsequently, the cohorts were balanced (entropy balancing and inverse probability of censoring) based on age, ISUP score, PSA before sRT, PSA recurrence vs. persistence, and pT and R status in surgery. Finally, biochemical recurrence-free survival (BRFS) and metastasis free survival (MFS) rates were compared. We defined biochemical recurrence as PSA nadir after sRT +0.2 ng/ml.

Results:

In total, 717 patients (control: 255, PSMA-guided: 462) with median follow-up of 75 (control) and 31 (PSMA-guided) months were included. The cohorts were well balanced with standardized mean differences <0.1 for all variables. In the control cohort, no patient had androgen deprivation therapy (ADT) and no sRT to elective pelvic lymph nodes (PLN) was performed. In the PSMA-guided cohort, 70 (82.2%) patients had PET-positive pelvic LNs, 85 (18.4%) patients received ADT and in 104 (22.5%) patients PLNs were irradiated. Three years BRFS rates were 71% (CI 64 – 78%) and 77% (CI 72 – 82%) for control patients and patients with PSMA-PET guided RT. The PSMA-PET group had favorable BRFS in the first year (HR 0.51, CI 0.28-0.93, p=0.027) and in 18-24 months (HR 0.32 CI 0.0.14-0.75, p = 0.009) after sRT. This effect diminished after 24 and 30 months of follow-up, respectively (HR 0.99-1.93, p>0.241). A sensitivity analysis was performed by excluding patients receiving ADT or missing irradiation of the prostatic fossa and comparable results were obtained. Patients in the PSMA-PET group had a lower rate of lymph node relapses after sRT (n=16/ 59.3% of patients with metastases within 3 years vs. n=22.6/85.1%, weighted SMD = 0.603) whereas local recurrences were comparable between both groups (weighted SMD = 0.025). MFS rates after 3 years (PSMA PET: 91.2% CI 88.1-94.4 and control: 89.2% CI 84.6-94.1) were comparable between both groups. In the PSMA guided cohort, 81% of patients had a second PSMA-PET in case of biochemical relapse following sRT. It is unknown how many patients in the control group had a PSMA-PET scan for re-staging following sRT.

Conclusion:

Our study suggests a significant improvement in short- and midterm BRFS with the inclusion of PSMA-PET for sRT guidance. One possible reason is the individualized coverage of regional lymphatic disease in the salvage radiotherapy field based on PET. MFS was not improved in the PSMA-PET group, which might be explained by the usage of PSMA-PET for re-staging after sRT. Currently, prospective studies with less patients included (n<450) are ongoing to validate this finding.

Keywords: prostate, PSMA PET, salvage radiotherapy

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Fecal incontinence after moderately hypofractionated VMAT fof localised prostate cancer

Joan Lozano 1 , Esther Jovell 2 , Nicolas Feltes 1 , Montse Colomer 1 , Maria Lizondo 1 , Manuel Galdeano-Rubio 1 , Saturio Paredes 1 , Esther Rubio 1 , Josep Maria Solé 1