ESTRO 37 Abstract book

ESTRO 37

S433

define a recurrence PTV (radiological GTV + 10 mm). Most patients were treated with three-dimensional conformal radiotherapy. Androgen deprivation was delivered based on the preferences of the attending physicians. Acute and late toxicity were scored according to the RTOG and CTCAE v4.0 scales. Results The median time to diagnosis of recurrence after radical prostatectomy was 38.8 months (2.39–171.50 months). The multiparametric-MRI was positive in 33p: Local: 26p; lymph nodes: 7p; both:1p. Most local recurrences occurred at the perianastomotic site. Median radiation doses in prostate bed, local recurrence PTV and positive lymph nodes were 70.2 Gy (50.4-73 Gy), 73Gy (70.2-75 Gy) and 60.30Gy (50.4-75.2 Gy) respectively. Thirty-two patients were treated with androgen deprivation for a median time of 6 months (6-36 months). With a median follow-up of 57 months (7-75 months) 15p (21.7%) had a biochemical relapse. Clinical relapse was detected in 8 patients: 1 local, 1 in the lymph nodes and 6 distant metastases. We observed acute grade 2 genitourinary (GU) toxicity in 4p (5.8%) and gastrointestinal (GI) toxicity in 13p (18.8%). No patient developed acute grade 3 toxicity. Grade 2 late GI toxicity occurred in 4p (5.7%) and grade 3 in 3p (4.2%). Grade 2 and 3 GU late toxicity was observed in 12 (18.4%) and 6 (9.2%) respectively. Late haematuria grade ≥2 was higher in those patients receiving more than 70 Gy (13% vs 1.5%;p=0.08). All the 6p with grade 3 haematuria were treated with doses higher than 70 Gy. Four of these patients could not be treated with full bladder due to postoperative incontinence (bladder mean dose > 65 Gy). One patient was under acenocoumarol treatment and the other one had and artificial urethral sphincter implanted. Only 3 patients were treated with IMRT. Conclusion Dose-intensified salvage radiotherapy after radical prostatectomy offered good biochemical control but resulted in an increased grade 3 late urinary toxicity. A careful selection of the patients and IMRT treatments may contribute to decrease this toxicity. PO-0830 Patterns of failure in a primary staging setting for prostate cancer evaluated with PSMA-PET imaging K. Schiller 1 , M. Devecka 1 , T. Maurer 2 , M. Eiber 3 , S.E. Combs 1 , G. Habl 1 1 Klinikum rechts der Isar- TU München, Klinik für Strahlentherapie und Radioonkologie, München, Germany 2 Klinikum rechts der Isar- TU München, Klinik und Poliklinik für Urologie, München, Germany 3 Klinikum rechts der Isar- TU München, Klinik für Nuklearmedizin, München, Germany Purpose or Objective 68 Ga-PSMA-PET-imaging can be considered as a highly sensitive and specific diagnostic element for p atients with prostate cancer (PC). Does the standard clinical target volume (CTV) according to the RTOG consensus cover the majority of 68 Ga-PSMA-PET detected lymph nodes in a primary/ definitive setting? Material and Methods 159 patients with PC, that received 68 Ga-PSMA-PET- imaging, in a primary setting, were screened and 25 elaborated in the process of this study. These 25 high-risk patients had a total of 126 LNs that showed enhancement on 68 Ga-PSMA-PET-imaging. A standard CTV according to the RTOG consensus was delineated and LNs were divided into two groups depending upon if they were inside or outside of that volume. Results Out of the 126 LNs, 81 (64.3%) were covered by the CTV translating into 11 out of 25 patients (44%) that had all detected LNs inside the respective radiation volume. LNs

Figure 1. Sagittal view of the generated volumes on the planning CT. Results The median follow-up was 64 months. The 5-years risk of urinary frequency (grade ≥ 2) was 9.3% (95%CI: 3.9- 14.7%). The upper third of the urethra, the basal point and the sphere 10 mm in diameter were significantly associated with the risk of late urinary frequency in high doses (V79 and V80), with a C-index ranging from 0.60 to 0.67 (Table 1). The most predictive and significant parameter was the basal point with a C-index at 0.67 (p = 0.007; HR = 1.015). The bladder, prostate, lower and middle third of the urethra were not significantly associated with the risk of urinary frequency. Table 1. Volumes significantly associated with the risk of late urinary frequency (grade ≥ 2). (Bladder and prostate were not significant) Conclusion High doses received in the urethro-vesical region appear predictive of late urinary frequency. These results need, however, to be confirmed in other cohorts. PO-0829 Postprostatectomy dose intensified salvage radiotherapy is associated with grade 3 late haematuria G. Sancho Pardo 1 , E. Acosta 1 , L. Tilea 1 , D. Hernández 2 , N. Farré 1 , J. Balart 1 , N. Jornet 3 , G. Gómez de Segura 1 , J. Craven-Bartle 1 1 Hospital de la Santa Creu i Sant Pau, Radiation Oncology, Barcelona, Spain 2 Hospital de la Santa Creu i Sant Pau, Radiology, Barcelona, Spain 3 Hospital de la Santa Creu i Sant Pau, Medical Physics, Barcelona, Spain Purpose or Objective After radical prostatectomy, dose-intensified irradiation may improve salvage radiotherapy results. We analysed the acute and late toxicity in patients treated with doses higher than 70 Gy. Material and Methods We performed a retrospective study in 70 patients (p) with prostate cancer who had biochemical failure after radical prostatectomy. All patients underwent a multiparametric -MRI to investigate the site of recurrence before planning the radiation treatment. Clinical and planning target volumes (CTV and PTV) were contoured according to the EORTC guidelines. Elective pelvic irradiation was indicated in patients without lymphadenectomy. In patients with visible recurrence we registered the mpMRI and the simulation CT images to