ESTRO 36 Abstract Book

S703 ESTRO 36 2017 _______________________________________________________________________________________________

with exception of PSA before PET/CT: Pts with PSA ≤ 0.2 ng/ml had a detection rate of 33.3%, with PSA 0.21 ≤ 0.5 ng/ml a rate of 41.2% and with PSA 0.51 ≤ 1.0 ng/ml a rate of 69.2% (figure 1). Median PSA before PET/CT in pts with pathological findings (n=92) was 1.90ng/ml and without (n=37) 0.30ng/ml, in newly diagnosed pts 12.4ng/ml, in pts with PSA relapse 0.49ng/ml and in pts with PSA persistence 0.99ng/ml. 68 Ga-PSMA PET/CT had a high detection rate of PCa recurrence outside the prostatic fossa in pts being considered for salvage RT (figure 2): 22.4% of these pts had PET-positive pelvic lymph nodes and 4.1% distant metastases. In pts considered for salvage RT with a PSA < 0.5 ng/ml 68 Ga-PSMA PET/CT still detected in 16.0% local recurrences within the prostatic fossa and in 20.0% PET-positive pelvic lymph nodes. 68 Ga-PSMA PET/CT had a significantly higher diagnostic value compared to the contrast enhanced CT scan. This resulted in a modification of RT in 56.6% of pts equally observed in high risk (59.2%) as in low/intermediate risk pts (53.8%) (p= 0.825).

To describe efficacy and safety of a single-fraction high- dose-rate brachytherapy (HDRBT) boost for patients diagnosed with NCCN intermediate and high risk prostate cancer using real-time transrectal ultrasound (TRUS) based planning in combination to external beam radiation therapy (EBRT) Material and Methods The records of 146 patients treated with a single-fraction HDRBT boost of 14 Gy using real-time TRUS based planning were reviewed. External beam radiation therapy (46 Gy/23 fractions or 50 Gy/25 fractions) was performed before (76%) or after (24%) HDRBT boost. Genito-urinary (GU) and gastro-intestinal (GI) toxicity were assessed according to CTCAE v4.0 every 6 months after the end of combined treatment, as well as PSA evaluation. Results The median follow-up was 30 months. Antiandrogen deprivation was administered in 53.6% of the patients. Thirteen patients (8.9%) experienced failure. The biological progression-free survival (bPFS) rate at 24 months was 94%. Ten patients experienced urinary retention within five days after treatment. There were two cases of grade 3 toxicity (rectal bleeding and dysuria). GI and GU toxicity was reported in 14.4% and 54% of the patients respectively. Conclusion Single-fraction HDRBT boost of 14 Gy using real-time TRUS in combination to pelvic EBRT is a feasible and promising treatment option for intermediate and high risk prostate cancer patients. EP-1325 Risk adapted dose-intensified postoperative Tomotherapy RT in prostate cancer using a SIB. M. Beck 1 , T. Barelkowski 1 , A.H. Thieme 1 , S. Wecker 1 , D. Kaul 1 , W. Wlodarczyk 1 , V. Budach 1 , P. Wust 1 , P. Ghadjar 1 1 Department of Radiation Oncology, Charite Universitätsmedizin, Berlin, Germany Purpose or Objective To evaluate a novel risk adapted dose-intensified postoperative radiation therapy (RT) scheme for patients A consecutive series of prostate cancer patients who received postoperative RT after radical prostatectomy (RP) using helical Tomotherapy between 04/2012 and 04/2015 were retrospectively analyzed. RT was administered using a simultaneous integrated boost (SIB) to the area at risk (37 fractions of 1.9 Gy, total dose: 70.3 Gy) being defined based on histopathological findings (T3 region, R1 region) and in a few cases according to additional diagnostic imaging information. The whole prostate bed was treated with a dose of 66.6 Gy (37 fractions of 1.8 Gy). Primary endpoints were acute and late genitourinary (GU) and gastrointestinal (GI) toxicities according to the National Cancer Institute Common Terminology Criteria version 4.0 (CTCAEv4.0). Secondary endpoints included patient reported outcome as assessed by the International Prostate Symptom Score (IPSS) and the International Consultation on Incontinence questionnaire (ICIQ), as well as biochemical recurrence defined as a prostate specific antigen (PSA) of 0.4 ng/ml and rising. Results A total of 69 patients were analyzed. Sixteen patients underwent adjuvant radiation therapy (ART) and 53 patients salvage radiation therapy (SRT), respectively. The median follow-up was 20 months (range, 8-41 months). Six (8.7%) and four (5.8%) patients experienced acute grade 2 GU and GI toxicity. Two patients (2.9%) had late grade 2 GU toxicity, whereas no late grade 2 GI nor any grade 3 acute or late GU or GI events were observed. When compared to the baseline urinary symptoms (p=1.0) and incontinence (p=0.9) were not significantly different at the end of follow-up. A total of seven patients (10.1%) with prostate cancer. Material and Methods

Conclusion The detection of PCa is strongly associated with PSA level at time of 68 Ga-PSMA PET/CT. 68 Ga-PSMA PET/CT differentiates local, regional and distant metastatic disease with considerable implications for disease management. 68 Ga-PSMA PET/CT narrows the diagnostic gap in post-prostatectomy pts with rising PSA ≤ 0.2 ng/ml considered for salvage RT.

EP-1324 Single-fraction HDR brachytherapy boost in combination to EBRT for prostate cancer A. HuertaS 1 , P. Blanchard 1 , L. Calmels 1 , M. Edouard 1 , A. Bossi 1 1 Gustave Roussy, Department of Radiation Oncology, Villejuif, France

Purpose or Objective