ESTRO 37 Abstract book

S867

ESTRO 37

between December 2015 and July 2017. All underwent BioProtect ® balloon implantation. A total dose of 3750 cGy in 5 consecutive days was performed. For dosimetric comparison, additional CT scans were performed pre balloon implantation. Maximum and average dose to the rectum, Vol(cc)>3440cGy, D10, D20 and D50 were calculated pre and post balloon implantation. EPIC QoL scoring index questionnaire for bowel habits and urinary function at the outset and at the end of the treatment course was obtained. Results A statistically significant reduction in the max and average dose to the rectum as well as in the Vol (cc)>3440cGy, D10 and D20 dosimetric parameters with p value <0,005 was obtained. D50 parameter had no statistical difference between pre and post balloon implant p value >0,08. No balloon placement related toxicities were observed in this study. EPIC QoL for bowel habits and urinary symptoms had no statistical difference between pre and post balloon implant. Conclusion Increased separation with a balloon spacer between rectum and prostate appears to be a safe and effective tool allowing for lower dose to the anterior rectal wall. Acute and late effects to the rectum with extreme hypofractionation may be underestimated, as limited data are available for these new regimens. The BioProtect ® balloon spacer has advantageous characteristics compared with other spacing solutions, in particular the amount of spacing achieved and the related homogeneity. This balloon spacer presents the possibility of adjustable placement (including deflation and repositioning) during the procedure, avoiding any asymmetric deployment, allowing for optimal spacing. A low level of toxicity for bowel habits and urinary function was observed for this cohort. Dosimetric improvements observed with lower doses to the rectum allows for extra dose to the prostate without exceeding this OAR tolerance, opening new possibilities for dose escalation and disease control. EP-1608 Prostate cancer radiotherapy in elderly patients : Does it make a difference in acute toxicities? M. Wafa 1 , N. Fourati 1 , K. Hajeur 1 , F. Leila 1 , S. Tarek 1 , K. Mouna 1 , S. Wicem 1 , D. Jamel 1 1 Hopital Habib Bourguiba, Radiation Oncology, Sfax, Tunisia Purpose or Objective The aim of our study was to retrospectively compare, the incidence of acute toxicities occurred during conformal radiotherapy, with curative intent in patients aged over 70 years and the younger population. Material and Methods From 2011 to 2016, 84 patients were treated with conformal radiotherapy for localized prostate cancer including 42 patients (50%) older than 70 years (group 1) and 42 patients younger than 70 years (group 2). For group 1, the median age was 74 years (70-81 years), the median PSA was 18.5 ng / ml (1-219 ng / ml). According to D'Amico classification, 29 patients (69%) were at high risk group. One patient (2.4%) had postoperative radiotherapy and 2 patients (4.8%) had lymph node involvement. For group 2, the median age was 64 years

(50-69 years), the median PSA level was 11 ng / ml (1-192 ng / ml). Twenty five patients (59.5%) were at high risk group. Five patients (11.9%) had postoperative radiotherapy and 3 patients (7.1%) had lymph node involvement. Treatment consisted on 3D conformal radiation therapy (n=46) or intensity modulated radiotherapy (n=38), at a dose of 66 Gy for postoperative irradiation and at a dose ≥ 70 Gy for the definitive treatment. Patients were followed up weekly during treatment to determine the acute toxicities which were graded according to the Common Terminology Criteria for Adverse Events (CTCAE) v.4. Khi-Deux test was used to compare the two groups and a p < 0.05 was considered statistically significant. Results Forty patients (95.2%) in group 1 had developed urinary toxicity which was greater or equal to grade 2 in 8 cases (19.1%). In group 2, 38 patients (90.5%) had developed urinary toxicity which was greater or equal to grade 2 in 9 cases (21.4%). The difference between the 2 groups was not significant (p = 0.39). Gastrointestinal toxicity was observed in 13 patients (30.9%) in group 1 and 23 patients (54.8%) in Group 2 with a significant difference (p = 0.02). This toxicity was greater or equal to grade 2 in 3 cases (7.1%) in group 1 and in 2 cases (4.8%) in group 2. Conclusion Curative treatment of prostate cancer in the elderly is controversial. In fact radical prostatectomy is rarely proposed to patients aged over 70 years. Conformal radiation therapy seems to be effective and well tolerated alternative for this population. Current published data show that high-dose radiation therapy (≥70 Gy) is not more toxic for older compared to younger subjects. The results of our study are consistent with the literature. Age should not be a limiting factor for conformal radiation therapy in curative intent for older patients. EP-1609 Circulating hematopoietic progenitor cells and endothelial cells in prostate cancer under SBRT C. Cigarral García 1 , L.I. Sánchez-Abarca Bernal 2 , C. Rodríguez Serrano 2 , V. Macías Hernández 1 , M.P. García Rodríguez 1 , M.C. Hernández Corral 1 , B. Vidriales Vicente 2 , F. Sánchez-Guijo Martín 2 , L.A. Pérez-Romasanta 1 1 IBSAL-Hospital Clínico Universitario de Salamanca, Radiation Oncology Department, Salamanca, Spain 2 IBSAL-Hospital Clínico Universitario de Salamanca, Hematology Department, Salamanca, Spain Purpose or Objective Blood circulating hematopoietic progenitor cells (CPCs) and circulating endothelial cells (CECs) are two cell groups that appear to play a key role in tissue vasculogenesis. Quantification by flow cytometry of CECs has been shown to have prognostic value in a number of neoplastic diseases. The quantification of CPCs and CECs after stereotactic-body-radiation-therapy (SBRT) for prostate cancer has not been established. This was the main objective of the current study. Material and Methods This prospective study was conducted on 10 patients diagnosed of prostate cancer that underwent SBRT in our Institution. Mean age was 71 years (range 58-76). The main SBRT schedule was 45.20Gy in 8Fx (BED 1.5 = 92.34Gy) delivered with IMRT in Tomotherapy unit in all cases. Endorectal balloon was used in all patients to limit prostate intra-fraction motion during treatment and to decrease the volume of rectum and anus receiving high dose radiation. Peripheral blood samples were collected