ESTRO 37 Abstract book

S864

ESTRO 37

EP-1601 PET imaging in patients with biochemical progression treated with high dose salvage radiotherapy R.M. D'Angelillo 1 , L.E. Trodella 1 , M. Fiore 1 , A. Iurato 1 , A. Carnevale 1 , C. Greco 1 , A. Sicilia 1 , M. Miele 1 , P. Trecca 1 , L. Trodella 1 , S. Ramella 1 1 Campus Biomedico University, Department of Radiation Oncology, Roma, Italy Purpose or Objective Biochemical recurrence after radical prostatectomy occurs in 15-50% of operated patients. Site of recurrence is generally unknown, and radiotherapy is generally adopted as salvage treatment with 60-66 Gy delivered to prostatic fossa. Dynamic 18F-Choline PET/CT could identify biological target volume (BTV), thus to ameliorate radiotherapy target definition and results. Material and Methods Data on 155 patients with biochemical progression after radical prostatectomy between January 2009 and December 2015 were reviewed. All patients at time of diagnosis of biochemical recurrence underwent to dynamic 18F-Choline PET/CT, which revealed in all cases a local recurrence. High-dose salvage radiotherapy (HD- SRT) was accordingly delivered up to total dose of 80 Gy to BTV. Toxicity was recorded according to CTC vers. 4.0 scale. Results The mean value of PSA before radiotherapy was 1.21 ng/ml. Treatment was generally well tolerated: 143 patients (92%) completed treatment without any interruption. Acute toxicity was: Gastro-intestinal (GI) in 62 patients (40%); Genito-urinary (GU) in 31 patients (20%). No grade > 3 acute toxicity was recorded. Late toxicity was: 16 events (10.3%) of grade 1 GU toxicity and 9 patients (5.8 %) with grade 1 GI. Three patients (1.9 %) experienced grade 2 toxicity (two gastro-intestinal and one genito-urinary toxicity). With a mean follow-up of 48 months 38/155 (24.5%) experienced a biochemical Dynamic 18F-Choline PET/CT could identify BTV in biochemical relapsed patients. HD-SRT delivered according to PET/CT data is safe and could validate ex- adiuvantibus the role of functional data overcoming the definition of biochemical recurrence. recurrence. Conclusion EP-1602 MPMRI planning in salvage radiotherapy of biochemical recurrence after radical prostatectomy S. Vukcaj 1 , G. Perugini 2 , R. Muni 1 , E. Iannacone 1 , S. Takanen 1 , F. Piccoli 1 , F. Filippone 1 , L. Maffioletti 1 , M. Kalli 1 , L. Feltre 1 , P. Ghirardelli 1 , G. Querques 2 , M. Roscigno 3 , L. Da Pozzo 3 , S. Sironi 2 , L. Cazzaniga 1 1 ASST Papa Giovanni XXIII, Radiotherapy, Bergamo, Italy 2 ASST Papa Giovanni XXIII, Radiology, Bergamo, Italy 3 ASST Papa Giovanni XXIII, Urology, Bergamo, Italy Purpose or Objective To describe how MPMRI can influence treatment decisions, target volumes delineation and dose prescription, in patients (pts) with biochemical recurrence after radical prostatectomy Material and Methods 11 pts with biochemical recurrence (PSA > 0.2 ng/ml or PSADT (Doubling Time) < 6 months) after radical prostatectomy were studied with MPMRI. Based on MPMRI findings we defined two groups of pts. In the first group (6 pts) MPMRI did not show any macroscopic recurrence so salvage radiotherapy (SRT) was delivered on prostate

bed according to the standard dose prescription (70Gy/35 frx, homogenously). In the second group (4 pts) MPMRI detected a macroscopic recurrence, defining two different PTVs and dose prescriptions: an High Risk (HR) volume (72 Gy/32 frx) and a Low Risk (LR) volume (64 Gy/32 frx). CTV HR corresponded to macroscopic recurrence and was defined by MPMRI-T2 images fusion with simulation CT, CTV LR was the remaining prostate bed. All treatments were conducted using Volumetric IMRT- Simultaneous Boost technique and daily IGRT. We used Student’s T-Test to compare intersection volume averages: rectum and PTV (HR and Standard), bladder and PTV (HR and Standard). Acute toxicity were assessed every weeks using the RTOG score.

Results The MPMRI was positive for macroscopic relapse in 36.36% (4 pts), PSA values at the time of biochemical recurrence varied from 0.15 ng/ml to 0.53 ng/ml and PSADT varied from 6 months up to >12 months. In 1 pt MPMRI showed, at the level of bladder-uretral anastomosis, a vegetative tissue thickening in the bladder lumen which was later histologically confirmed to be normal prostatic tissue, so no SRT was planned and the value of PSA (0,15 ng/ml) remained stable. MPMRI was negative for macroscopic recurrence in 45.45% (5 pts), therefore we performed standard SRT at prostate bed (PSA values at the time of biochemical recurrence also ranged from 0.15 ng/ml to 0.46 ng/ml and PSADT varied from 3 to 12 months).In another pt MPMRI detected a dubious macroscopic recurrence in the prostate bed and a femoral head metastasis, subsequently not confirmed by PET choline, so SRT was performed as standard. The value of PSA at time of biochemical recurrence was 0.26 ng/ml. The mean volumes of intersection between rectum and HR- PTV were smaller than the mean intersection volumes of the rectum and Standard PTV (p=0.0166). The same occurred for the mean volumes of intersection between bladder and HR PTV than bladder and Standard PTV (p=0.0119). No cases of acute toxicity were reported in the two groups.