ESTRO 38 Abstract book

S446 ESTRO 38

I. San Miguel 1 , D. Büchser 1 , F. Suarez 1 , F. Casquero 1 , I. Fernandez 2 , E. Rodeño 2 , R. Ortiz de Zarate 1 , R. Llarena 3 , J. Garcia Olaverri 3 , L. Martinez-Indart 4 , P. Bilbao 1 , A. Gomez De Iturriaga 4 1 Cruces University Hospital, Radiation Oncologist, Baracaldo, Spain ; 2 Cruces University Hospital, Nuclear Medicine, Baracaldo, Spain ; 3 Cruces University Hospital, Urology, Baracaldo, Spain ; 4 Cruces University Hospital / Biocruces Health Research Institute, Radiation Oncologist, Baracaldo, Spain Purpose or Objective A better knowledge of the pattern of recurrence after metastases directed therapy (MDT) in patients with oligometastatic disease might be useful to select the most appropriate candidates. The aim of this study is to report in a prospective cohort of oligorecurrent prostate cancer patients factors associated with the pattern of relapse and disease control after MDT. Material and Methods From 2012 to 2017, 104 lesions diagnosed with Ch-PET in 53 consecutive oligometastatic-recurrence prostate cancer patients have been treated. Biochemical failure was defined using the nadir+2 ng/mL definition; a DFS event was defined as evidence of disease by any clinical, pathological or radiological method. Reassessment with Ch-PET imaging was performed in case of biochemical failure or if clinically indicated to rule out local or distant metastatic progression. Patterns of first progression following MDT were recorded. In case of an oligometastatic recurrence outside the previous PTV field, a retreatment with SBRT or IMRT was offered. Descriptive analyses were done. Chi-square and Fisher-exact tests were performed to evaluate the influence of patient, tumor, and treatment characteristics on the pattern of relapse. A p<0.05 considered statistically significant Results The different subsites of metastatic involvement before 1 st MDT were lymph-nodes in 67.9% and bone in 32.1% of patients. The treatments administered to the initial oligo- recurrence sites were IMRT (49%) and SABR (51%) +/- short course ADT. After a median follow-up of 28 months (6-54 months), 89% of the patients remain alive and only 3 deaths were related to prostate cancer. At last follow-up 34% of the patients were free from disease progression. Twenty-five patients with biochemical failure after 1 st MDT presented distant recurrence on re-staging Ch-PET and 64% (16/25) were again oligometastatic relapses allowing for a 2 nd MDT in 12 patients. In terms of relapse site, 7/7 (100%) patients with initial bone disease presented a subsequent bone relapse, 10/18 (56%) patients with initial nodal disease presented a nodal relapse and 8/18 (44%) a bone relapse. At diagnosis, a PSA pre-PET<4.5ng/mL was associated with higher probability of presenting with nodal oligometastases (p=0.049). The variables with significant association with nodal relapse after MDT were a pre-MDT PSA<10ng/mL (p=0.049) and initial nodal oligometastatic site (p=0.02). A PSADT>12 months before MDT was the only factor statistically associated with higher disease control (p=0.011). Conclusion Long-term disease control is still possible in oligometastatic patients who receive MDT. At relapse, most patients are again oligometastatic allowing for repeated MDT. The pre-MDT PSA and initial nodal oligometastatic site are associated with a further nodal relapse. Patients presenting with a PSADT>12 months and a PSApre-PET<4.5ng/mL may have a better prognosis. PO-0850 Comparison of self-reported acute urinary incontinence in pts treated with adjuvant or salvage IMRT F. Munoz 1 , D. Cante 2 , E. Garibaldi 3 , A. Peruzzo 4 , E. Petrucci 5 , E. Delmastro 3 , G. Sanguineti 6 , A. Faiella 6 , B.

Day 9(Coho rt 1)

Day 9 (Coho rt 2) 32 ± 407 87 ± 34 10.5 ± 3.9

Baseline(Coh ort 1)

Baseline(Coh ort 2)

PSA (median)ng /m

31 ± 23 53 ± 257

52 ± 82

SUV max

23 ± 14

14 ± 10 52 ± 23

SUV mean 6 ± 3.6

4 ± 3.5 7.7 ± 2.2

Total volume (mls)

28 ± 40

12 ± 48 290 ± 1141 290 ± 1585

Conclusion PSMA is a manipulable receptor with rapid dichotomous in- vivo response on PSMA PET to androgen blockade dependent on hormone sensitive versus castrate resistant PCa phenotype. This has important implications for the interpretation of PSMA PET imaging, and in the timing/sequencing of PSMA targeted therapy. PO-0848 Early mortality of prostatectomy vs. radiotherapy as a primary treatment for prostate cancer D. Medenwald 1 , K. Medenwald 1 , A. Glowka 1 , D. Vordermark 1 , C. Dietzel 1 1 Martin Luther University Halle-Wittenberg, 1\tDepartment of Radiation Oncology, Halle/Saale, Germany Purpose or Objective To assess the extent of early mortality and its temporal course after prostatectomy and radiotherapy in the general population. Material and Methods Data from SEER-database and German epidemiologic cancer registries were used for the years 2005-2013. Metastasized cases and deaths from bladder cancer were excluded (avoiding incidental cases after bladder cancer). Analysing overall mortality, year-specific Cox regression models were used for German and US-American data after adjusting for age (including age squared), risk stage and grading. To estimate temporal hazards we computed year- specific conditional hazards for surgery and radiotherapy after propensity-score matching and applied constant proportional hazard models. Results In German and US-American populations we observed higher initial three-month mortality odds for prostatectomy (USA: 7.4-fold risk, 95% CI: 6.1-9.0; Germany: 8.5, 95% CI: 4.5-16.0) approaching the null effect value not before 20 months after diagnosis (used as a cut-off for the observational period defining early mortality). During the observational period we observed an increasing hazard ratio for the 20-month mortality in the US- population (2005: 1.4, 95% CI: 1.2-1.6; 2013: 1.8, 95% CI: 1.4-2.1) for the surgery/radiotherapy comparison. In the German population the effect remained virtually constant (2005: 1.5, 95% CI: 1.0-2.3; 2013: 3.4, 95% CI: 2.1-5.7). Considering low-risk cases, the adverse surgery effect appeared stronger. Conclusion There is strong evidence from two independent populations of a considerably higher early mortality after prostatectomy compared to radiotherapy extending the time of early mortality considered by previous studies up to 20 months. PO-0849 Pattern of Relapse After Metastases Directed Therapy in Oligorrecurrent Prostate Cancer