ESTRO 2020 Abstract Book

S613 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

radiation therapy (MH-IMRT) regimen of 72 Gy in 30 fractions over 6 weeks in an East Asian population. Material and Methods The outcomes of 412 consecutive prostate cancer patients who received MH-IMRT between May 2007 and December 2012 were reviewed retrospectively. The median patient age was 70.9 (range, 50–84) years. According to the NCCN criteria, 41 (10.0%) patients were classified as low-risk, 150 (36.4%) as intermediate-risk, 185 (44.9%) as high-risk, and 36 (8.7%) as very high-risk. Neoadjuvant and adjuvant androgen deprivation therapy was delivered to 296 (71.8%) and 190 (46.2%) patients, respectively. Late gastrointestinal (GI) and genitourinary (GU) toxicity rates were evaluated according to the Common Terminology Criteria for Adverse Events ver. 3.0. The overall survival, biochemical relapse-free survival rate (bRFS), late GI toxicity, and GU toxicity rates were analyzed with the Kaplan–Meier method. Results The median follow-up duration was 71.5 (range, 1.4–124.8) months. The 5-year bRFS rate was 93.2%. For patients with low-risk, intermediate-risk, high-risk, and very high-risk disease, the 5-year bRFS rates were 100%, 93.9%, 93.6%, and 80.3%, respectively. The 5-year grade ≥2 late GI and GU toxicity rates were 3.3% and 4.5%, respectively. Conclusion The study results suggest an MH-IMRT regimen of 72 Gy in 30 fractions was effective and safe for the treatment of prostate cancer in an East Asian population. PO-1165 Toxicity and outcomes of postoperative hypofractionated Helical Tomotherapy for prostate cancer F. Cuccia 1 , G. Ferrera 2 , V. Serretta 3 , G. Mortellaro 2 , F. Verderame 4 , A. Lupo 5 , D. Cespuglio 2 , L. Ognibene 6 , G. De Gregorio 1 , E. Quartuccio 1 , A. Gioia 1 , M. La Vecchia 1 , N. Luca 1 , G. Trapani 1 , V. Valenti 1 , A. Tripoli 1 , A. Lo Casto 7 1 University of Palermo, Radiation Oncology School, Palermo, Italy ; 2 ARNAS Civico Hospital, Radiation Oncology, Palermo, Italy ; 3 University of Palermo, Department of Surgical- Oncological and Oral Sciences, Palermo, Italy ; 4 Hospital Vincenzo Cervello, Department of Hematology and Oncology, Palermo, Italy ; 5 ARNAS Civico Hospital, Urology, Palermo, Italy ; 6 San Gaetano Radiotherapy and Nuclear Medicine Center, Radiotherapy Unit, Bagheria PA, Italy ; 7 University of Palermo, Section of Radiology - Di.Bi.Med., Palermo, Italy Purpose or Objective PURPOSE: The role of hypofractionation in prostate cancer is well established for the definitive setting, while it is still investigational in the post-surgery scenario. The present study reports acute and late toxicities and biochemical control rates in a retrospective series of 107 patients with prostate cancer who were treated in the post-operative setting with moderate hypofractionation delivered by METHODS: From April 2013 to August 2018, 107 patients, with median age 68 years (range, 54-84), received post- operative radiotherapy, delivering to prostate bed a total dose of 63.8 Gy (EQD2=67.4 Gy) using 2.2 Gy fractions. Adjuvant treatment (n=54) was proposed within 6 months after surgery for patients with PSA ≤0.2 ng/ml in presence of adverse features like positive margins, extracapsular extension, seminal vesicles invasion or lymph nodal involvement. Salvage therapy (n=53) was delivered 6 months after prostatectomy in case of PSA≥0.2 ng/ml or for patients with persistent post-surgery PSA. In 67% of patients, in presence of pathological adverse features (pN+, inadequate lymph nodal dissection (<10 nodes), and/or Gleason Score>8) pelvic irradiation was administered with a median dose of 49.3 Gy (range, 48- 55.1 Gy) in conventional fractionation. Concurrent hormonal therapy was prescribed in 49.5% of cases. Acute Helical Tomotherapy. Material and Methods