S1279
Clinical - Urology
ESTRO 2026
A total of 65 patients who received sRT for BCR between 2019 and 2024 were retrospectively evaluated. All patients underwent 68Ga-PSMA PET-CT before RT. Patients with distant metastases or incomplete follow-up were excluded. The highest SUVmax value reported on PET-CT was recorded. All patients received conventionally fractionated sRT. Biochemical recurrence-free survival (bRFS) and distant metastasis-free survival (DMFS) were estimated using the Kaplan-Meier method, and prognostic factors were assessed with Cox regression analysis. Correlations were examined using Spearman's test with p<0.05 considered significant. Results: The median age at diagnosis was 64 years (range:46– 78), and the median follow-up duration was 17.3 months (range:1.5–65). Patient and treatment characteristics are summarized in Table 1. The median PSA at recurrence was 0.54 ng/mL, the median time to recurrence was 13.5 months (range:3-177), and the median time to PSA-nadir after RT was 2.8 (range:1-30) months. PSMA uptake was observed in 28 (43%) of patients prior to RT. Higher SUVmax values were associated with longer time to PSA-nadir (Pearson’s rho=0.5, p=0.004). The optimal cutoff for SUVmax in predicting delayed PSA-nadir (>2.8 months) was 6 (sensitivity 64%, specificity 50%). Patients with time to PSA-nadir >2.8 months experienced higher rates of biochemical recurrence (26% vs. 3%, p=0.008). During follow-up, biochemical recurrence and distant metastasis were observed in 14% and 9% of patients, respectively. Median bRFS and DMFS were not reached; 1-, 3-, and 5-year bRFS rates were 94%, 74%, and 62%, while DMFS rates were 94%, 90%, and 55%. The recurrence pattern identified by PSMA PET-CT (local, regional, or both) was not associated with bRFS (p>0.05). However, patients with PSMA-avid lesions had significantly lower bRFS compared to those without uptake (2-year 14% vs. 0%, p=0.002), with no significant difference in DMFS (p=0.08). Univariable and multivariable analyses are presented in Table 2.
patient numberGTV hypoxic fraction (rOEF>70%) at planning (%)GTV hypoxic fraction (rOEF>70%) at last fraction (%)difference hypoxic fraction (rOEF>70%) (%)114.80.61-14.220.620.32- 0.331.773.812.05461.3441.57-19.77592.9879.98-13 Conclusion: T2 mapping, T2* mapping, and IVIM MRI sequences show promise for generating rOEF as a surrogate marker of hypoxia in kidney tumors. The mean rOEF in the healthy kidney remained stable, while radiation decreased rOEF in tumors with initially high rOEF values; however, it had no significant effect on tumors with low baseline rOEF values. Keywords: Hypoxia, Renal cell carcinoma, radiation therapy Prognostic Significance of 68 Ga-PSMA PET-CT SUVmax in Patients Undergoing Salvage Radiotherapy for Prostate Cancer Pantea Bayatfard 1,2 , Cigdem Soydal 3 , Yasemin Celik 1 , Yuksel Urun 4 , Sumer Baltaci 5 , Serap Akyurek 1 1 Radiation Oncology, Ankara University, Ankara, Turkey. 2 Radiation Oncology, Denizli Onkolmer, Denizli, Turkey. 3 Nuclear Medicine, Ankara University, Ankara, Turkey. 4 Medical Oncology, Ankara University, Ankara, Turkey. 5 Urology, Ankara University, Ankara, Turkey Digital Poster 3929 Purpose/Objective: Salvage radiotherapy (sRT) represents the standard treatment approach for patients with biochemical recurrence (BCR) after radical prostatectomy. However, predictive biomarkers for treatment response in this setting remain limited. This study aimed to evaluate the prognostic role of SUVmax measured on 68Ga-PSMA PET/CT performed for restaging prior to sRT. Material/Methods:
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