ESTRO 38 Abstract book

S841 ESTRO 38

statins versus non-statins treated patients BFFS at 97 months was 74.6% versus 79% (p=0,31) and DFFS was 88% versus 87.2% (p=0.90). BFFS and DFFS in patients receiving ≤ 20mg/day vs ≥ 20mg/day of statins was 69.4% versus 77.8% (p=0.28) and 87.2% versus 88.3% (p=0.82), respectively.

Conclusion Daily ERB application during EBRT for the treatment of localized prostate cancer may reduce GI toxicity ≥ grade 2. However, the results above must be interpreted cautiously since the group of patients treated with ERB were all treated in the same center. Additional local protocol variations could have been confounders in the relation between ERB and GI toxicity. Further evaluation of the dosimetric parameters is necessary. EP-1557 Do metformin and statins play a role in localized high-risk prostate cancer? G. Cadeddu 1 , F. López Campos 1 , M. Martín Martín 1 , L. Pelari Mici 1 , K. Ytuza Charahua de Kirschner 1 , A. Hernández Corrales 1 , E. Carrasco Esteban 2 , S. Sastre Gallego 3 , I. Císcar García 1 , S. Sancho García 1 , A. Hervás Morón 1 1 Hospital Ramón y Cajal, Radiation Oncology, Madrid, Spain ; 2 Hospital Central de la Defensa "Gómez Ulla", Radiation Oncology, Madrid, Spain ; 3 Hospital Beata María Ana, Radiation Oncology, Madrid, Spain Purpose or Objective There is increasing evidence that statins and oral anti- diabetic drugs, such as metformin, can have a favourable role in the treatment of advanced prostate cancer. This study analyses the impact of metformin and/or statins on biochemical failure-free survival (BFFS) and on distant failure-free survival (DFFS) in high-risk prostate cancer treated with radiotherapy. Material and Methods From 2002 to 2016, 393 patients with histologically confirmed high-risk prostate cancer defined by National Comprehensive Cancer Network (NCCN) risk group were retrospectively evaluated. All patients assumed androgen deprivation therapy and were treated with radiotherapy according to the institution protocol. Biochemical recurrence was determined by Phoenix criteria defined as a PSA rise of 2 ng/mL or more above the nadir PSA, metastatic patients were defined by the presence of radiological documented metastasis (CT scan, MRI, Choline-PET or bone scintigraphy) in nodes, bones, or visceral disease according to RECIST 1.0 criteria. Association with BFFS and DFFS was analysed using Kaplan and Meier method. Results 393 patients with a median age of 70 years (46-83) and median PSA at diagnosis of 34ng/ml (0.6-766) were studied. Of the patients included in this study, 40% (N=158) were treated with statins (64.6% with a dose ≤ 20mg/day) and 16% of patients (N=63) were treated with metformin (77.4% with a dose ≤ 1700mg/day). With a median follow-up of 97 months, no statistically significant differences were found in BFFS and DFFS between patients treated with metformin versus non-metformin treated patients: 74% versus 77% (p=0.92) and 89% versus 87% (p=0.52), respectively. BFFS and DFFS in patients receiving ≤ 1700mg/day versus ≥ 1700mg/day of metformin was 78% versus 56% (p=0.10) and 93% versus 71% (p=0.12), respectively. Regarding patients treated with

Conclusion Metformin and statins treatments were not associated with an improvement of BFFS and DFFS in our analysis. Prospective studies are needed to define the role of metformin and statins in localized prostate cancer patients EP-1558 Updated results of a Phase II study on 5 fractions FFF SBRT for low and intermediate prostate cancer F. Alongi 1 , L. Nicosia 1 , R. Mazzola 1 , N. Giaj-Levra 1 , F. Ricchetti 1 , V. Figlia 1 , M. Rigo 1 , G. Sicignano 1 , S. Naccarato 1 , R. Ruggieri 1 1 Ospedale Sacro Cuore "Don Calabria", Radiation Oncology, Negrar, Italy Purpose or Objective SBRT had been shown to be a potential treatment option for localized prostate cancer (PC) in selected population. Usually, prostate SBRT has been delivered every other day in order to favour normal tissues recovery, minimizing side effects. Flattening Filter Free (FFF) delivery is a treatment modality able to reduce treatment beam-on time, decreasing patient positioning uncertainties. We reported feasibility, side effects and biochemical control of FFF SBRT delivered in 5 consecutive days in a cohort of patients affected by localized PC. Material and Methods The study, approved by Ethical Committee, started on January 2014. Inclusion criteria were: age ≤ 80 years, World Health Organization performance status ≤ 2, histologically proven prostate adenocarcinoma, low-to- intermediate risk according to D'Amico criteria, no distant metastases, no previous surgery other than TURP, no other malignant tumor in the previous 5 years, a pre-SBRT International Prostatic Symptoms Score (IPSS) ranged between 0 and 7. The SBRT-schedules were: 35Gy for low risk and 37.5Gy for intermediate risk PC in 5 fractions, delivered in 5 consecutive days. SBRT was delivered with volumetric modulated radiation therapy (VMAT). Toxicity assessment was performed according to CTCAE v4.0 scale. Neoadjuvant/concomitant hormonal-therapy was prescribed according to risk classification. Results