ESTRO 2020 Abstract book

S660 ESTRO 2020

PO-1163 68Ga-PSMA PET-Guided metastases directed stereotactic body radiotherapy in prostatic cancer patients M. Rigo 1 , R. Mazzola 2 , V. Figlia 2 , L. Nicosia 2 , N. Giaj- Levra 2 , F. Ricchetti 2 , C. Francesco 2 , F. Alongi 2 1 IRCCS Sacro Cuore Don Calabria Hospital- Cancer Care Center, Advanced Radiation Oncology Department, Negrar di Valpolicella VR, Italy ; 2 IRCCS Sacro Cuore Don Calabria Hospital- Negrar-Verona- Italy, Advanced Radiation Oncology Department, Negrar, Italy Purpose or Objective To investigate the efficacy and toxicity of 68 Ga-PSMA- Positron Emission Tomography-Computed Tomography (PET-CT)-guided stereotactic radiotherapy (SBRT-IGRT) in the treatment of prostate cancer oligometastatic recurrences after primary treatments. Material and Methods Sixty-five prostate cancer patients with biochemical relapse (44 castration-sensitive and 21 castration- resistant) were treated with Volumetric Modulated Arc Therapy and Image-Guided RT (VMAT-IGRT) on ≤5 metastastatic sites detected by 68 Ga PSMA PET-CT. Androgen deprivation therapy was continued in castration resistant (CR) patients. Biochemical control was evaluated with EORTC (European Organization for Research and Treatment of Cancer) and Phoenix definition. Toxicity was assessed according to CTCAE-criteria v. 4.03. Results A total of 166 metastases in 65 patients were treated with SBRT. The involved sites were pelvic lymph or para-aortic nodes (n = 105), bone (n = 48), prostatic bed or seminal vesicles (n = 11), lung metastases (n = 1) and abdominal wall nodule (n = 1). The median PSA value prior to RT was 0.65 ng/mL (range 0.10 – 11.08 ng/mL), the median PSA- doubling time was 5.5 months (range 0.61 – 140) and the median PSA post-RT was 0.63 ng/mL (range 0.01 - 13.55 ng/mL). A median dose of 35 Gy (range 18 – 70 Gy) was delivered in 2–10 fractions (the median BED 2Gy was 144 Gy). At a median follow-up of 14 months (range 3 – 34 months) all patients were alive, whereas 24 out of 65 patients irradiated (37%) were in remission and 41 were in progression (63%). In particular, 16 out of 21 castration resistant (CR) patients (76%) and 25 out of 44 castration sensitive (CS) patients (57%) were in progression. The actuarial 1-year LC, PFS and CSS rates were 92, 38 and 100%. At the ROC curve analysis a PSA nadir <0.25 ng/ml was correlated to distant metastases free survival (DMFS). At the univariate analysis DMFS was significantly longer for patients with PSA nadir <0.25 ng/ml (p=0.0). The median systemic treatment free survival was 19 months (range 13 - 24 months). No patient experienced grade ≥3 acute gastrointestinal or urinary toxicity. Conclusion By providing optimal LC, low toxicity and a promising PFS, 68 Ga PSMA PET-CT-guided metastases directed SBRT may be considered a promising treatment strategy in patients with oligometastatic prostate cancer, with an acceptable toxicity profile and allowing to postpone systemic therapies burdened by higher side effects. In our analysis reaching of PSA nadir <0.25 ng/mL was associated with improved DMFS and could serve as a surrogate endpoint for metastases directed stereotactic body radiotherapy. PO-1164 Long-term outcomes of radiotherapy regimen of 72 Gy in 30 fractions for prostate cancer K. Tamari 1 , R. Oh 2 , H. Shiomi 2 , S. Osamu 1 , K. Ogawa 1 1 Osaka University Graduate School of Medicine, Radiation Oncology, Suita- Osaka, Japan ; 2 Miyakojima IGRT Clinic, Radiation Oncology, Osaka, Japan Purpose or Objective To evaluate the long-term efficacy and safety of moderately hypofractionated intensity-modulated

PO-1162 Post hifu salvage radiotherapy in locally relapsed prostate carcinoma: a mono-institutional analysis M. Rigo 1 , R. Mazzola 2 , G. Napoli 2 , N. Giaj-Levra 2 , V. Figlia 2 , L. Nicosia 2 , F. Ricchetti 2 , C. Bellorofonte 3 , F. Cuccia 2 , F. Alongi 2 1 IRCCS Sacro Cuore Don Calabria Hospital- Cancer Care Center, Advanced Radiation Oncology Department, Negrar di Valpolicella VR, Italy ; 2 IRCCS Sacro Cuore Don Calabria Hospital- Cancer Care Center- Negrar- Verona- Italy, Advanced Radiation Oncology Department, Negrar, Italy ; 3 Columbus Clinic Center, Urology, Milano, Italy Purpose or Objective To evaluate tolerance, feasibility and biochemical control rates of salvage external beam radiotherapy (EBRT) in patients with local relapse from prostate cancer after high intensity focused ultrasound (HIFU) as primary treatment. Material and Methods This is a retrospective analysis of 24 patients with histological proven prostate adenocarcinoma treated with 1 or more HIFU sessions between 2007 and 2018. All patients presented biochemical failure after HIFU (according to the Stuttgard definition) and so 11C choline PET or 68Ga/18F PSMA PET was performed for restaging and treatment planning. The median interval between HIFU and EBRT was 39 months (3 – 136 months) and the median PSA before EBRT was 6.94 ng/mL (2.07 – 91 ng/ml). Salvage EBRT was performed with moderate hypofractionation schedule in 28 fractions (n=16) or with extreme hypofractionation schedule in 5 fractions (n=8) by means image-guided volumetric modulation arc therapy (VMAT-IGRT). All patients were treated with EBRT to the residual prostate. In case of moderate hypofractionation (MHRT), the median dose was 71.4 Gy (71.4 -74.2 Gy) and 7 patients concomitantly received pelvic lymph node EBRT (50.4 – 51.8 Gy). In case of extreme hypofractionation (SBRT), the residual prostate with a median dose of 32.5 Gy (30 – 35 Gy) was irradiated. Five patients (21%) received concomitant/adjuvant androgen deprivation therapy (ADT). Primary endpoints were feasibility and toxicity associated to hypofractionated EBRT after HIFU failure. Genito-urinary (GU) and rectal and bowel toxicity (GI) were scored by common terminology criteria for adverse events version 4 (CTCAE V.4) scale. Biochemical response was assessed by ASTRO Phoenix criteria. Results The median follow-up after EBRT was 28 months. The median PSA nadir was 0.26 ng/mL (0.01- 12.05 ng/ml) and it was obtained in a median of 17 months. In case of moderate hypofractionation, the median PSA nadir was 0.15 ng/mL (0.01 – 2.48 ng/mL) and occurred within a median time of 19 months (3 – 59 months). In case of extreme hypofractionation, the median PSA nadir was 0.64 ng/mL (0.12 – 12.05 ng/mL) and occurred within a median time of 8 months (3 – 27 months). No grade 3 higher acute or late toxicity after EBRT was observed. Only 3 patients presented with G2 acute gastrointestinal toxicity (actinic proctitis), out of them one was treated with extreme hypofractionation. Twelve (50%) of patients experienced acute G1 GU toxicities: 8/16 of men treated with moderate hypofractionation and 4/8 of men treated with extreme hypofractionation. At the time of follow-up a complete local control of disease was achieved in 23/24 patients (96%). Conclusion Our data confirm the feasibility and the low toxicity of salvage EBRT with both schedules of treatment after HIFU failure. The findings of low acute toxicity and good biochemical control rates are encouraging, but larger number of patients and a longer follow-up are needed to confirm these results.