ESTRO 2021 Abstract Book

S643

ESTRO 2021

Associations between groups and 10-year DFS were highly significant on log-rank test (p<0.0001). Table 2 compares probabilities of 10-year DFS by 4YrPSA category with those reported by Crook et al. TABLE 2: 4-year PSA (ng/ml) ECC (95% CIs) Crook et al. (95% CIs) ≤0.2 97.5% (95.4-99.6) 98.7% (98.3-99.0) 0.2 to ≤0.5 89.0% (82.4-96.1) 93.5% (91.0-95.3) 0.5 to ≤1.0 81.5% (70.5-94.2) 85.9% (80.6-89.8) >1.0 41.8% (29.7-58.9) 48.0% (41.8-53.8) Sensitivity/specificity of 4YrPSA≤0.2ng/ml for 10-year DFS were 62.1% and 88.5% respectively. Conclusion Relapse rates were broadly similar, but slightly higher across all groups than those reported by Crook et al. Nonetheless, patients with 4YrPSA ≤0.2 had excellent outcomes, and this threshold was both sensitive and specific for predicting 10-year DFS. These data validate the findings of Crook et al. in a large UK cohort; 4YrPSA is a good predictor of long-term outcome following LDR-BT for PCa. PD-0810 Salvage Therapies for PSMA PET/CT-positive nodal-only recurrent prostate cancer: Impact on survival, functional outcomes and health-related quality of life N. Schmidt-Hegemann 1 , C. Trapp 1 , P. Rogowski 1 , C. Eze 1 , J. Milow 2 , A. Buchner 2 , M. Li 1 , H. Ilhan 3 , V. Wenter 3 , C.G. Stief 2 , C. Belka 4 , A. Kretschmer 2 1 Ludwig-Maximilians-Universität , Radiation Oncology , Munich, Germany; 2 Ludwig-Maximilians-Universität , Urology , Munich, Germany; 3 Ludwig-Maximilians-Universität , Nuclear Medicine , Munich, Germany; 4 Ludwig- Maximilians-Universität , Radiation Oncology, Munich , Germany Purpose or Objective The role of salvage lymph node dissection (SLND) in the management of nodal-only recurrent prostate cancer (PC) remains controversial. While unfavorable long-term oncological outcomes have cast doubt in the value of SLND as monotherapy in this clinical setting, comparative data with salvage lymph node radiation therapy (SLNRT) as a therapeutic alternative is rare. In addition, impact on health-related quality of life (HRQOL) has not been adequately evaluated yet. In the current study, we analyzed oncological as well as functional outcomes of patients with nodal-only recurrent PC treated with SLND or SLNRT in a single academic tertiary care center. Materials and Methods Local ethics committee approval was obtained. Analysis was limited to patients that were diagnosed with nodal-only recurrent PC via PSMA-PET/CT. SLND was performed via open approach. Regarding SLNRT, radiotherapy dose regimens were normo- or slightly hypo-fractionated and a boost to the PET-positive local recurrences within prostatic fossa and lymph nodes was applied simultaneously. Questionnaires were sent to obtain functional and oncological outcomes. EORTC QLQ-C30 and PR-25 questionnaires were used to assess HRQOL. Continence status was assessed using daily pad usage and the validated ICIQ-SF questionnaire. For multivariable analysis, cox regression models were used (p<0.05). Results 138 patients (SLND: 71; SLNRT: 67) fulfilled the inclusion criteria and were included in the current analysis. Median follow-up (FU) was 47mo for SLNRT patients (IQR 40 – 61), and 33mo for SLND patients (IQR 20–49; p<0.001). Peri-interventional androgen deprivation therapy (ADT) was administered to 89.6% in the SLNRT