ESTRO 36 Abstract Book

S716 ESTRO 36 _______________________________________________________________________________________________

2.91, p =0.005). Acute genitourinary adverse event (grade ≥ 2) was similar among the groups (RR=1.02, 95% CI: 0.92- 1.14, p =0.671). Gastrointestinal (RR=1.17, 95% CI: 0.90- 1.51, p =0.238) or genitourinary (RR=1.11, 95% CI: 0.94- 1.30, p =0.228) late adverse event (grade ≥ 2) data were not significant differences between two radiotherapy schedules. No publication bias was detected in this meta- analysis (all p ＞ 0.05). Conclusion Hypofractionated radiotherapy in intermediate- to high- risk localized prostate cancer was not superior to conventional radiotherapy and showed higher acute gastrointestinal adverse event in this meta-analysis. However, these findings should be utilized cautiously when directed in clinical treatment due to some limitations. EP-1336 Effect of bladder,trigone,urethra doses on acute genitourinary toxicity in prostate cancer treatment L.Z. Arican (Turkey), N. Akturk, K. Meltem, B. Aydin, H. Ellidokuz, I. Bilkay Gorken 1 Dokuz Eylul Univ. Health Sciences Institute, Department of Radiation Oncology, IZMIR, Turkey 2 Dokuz Eylul Univ. Health Sciences Institute, Department of Preventive Oncology, IZMIR, Turkey Purpose or Objective To evaluate the relationship between acute GUS toxicities and the dose/volume values of the bladder, trigone, urethra in prostate cancer(PCa) patients who were treated by volumetric modulated arc therapy(VMAT). Material and Methods Twenty seven moderate/high-risk PCa patients who were treated between January 2014 and November 2015 were retrospectively evaluated. According to the D’Amico classification 59% of the patients were at high risk. All patients recieved hormonotherapy (2-4 months neo/6-24 months adjuvant).Simulation was performed with a full bladder and empty rectum. Total doses of peripheral lymphatic, seminal vesicle and prostate were 56, 65 and 78 Gy in 37 fractions,respectively. Image guided radiotherapy was performed. The urethra, bladder and trigone were re-contoured respectively on planning CT fused with magnetic resonance images obtained before treatment. The minimum,maximum,mean and Vdose(V20- 80) values of the bladder, trigone and urethra were obtained. Acute GUS toxicites were graded according to RTOG. Age,history of previous abdominal surgery,TUR- P,diabetes,smoking, target and bladder, trigone and urethra volumes were evaluated as factors that affect grade ≥2 GUS toxicity. The Chi-square, ROC,Mann-Whitney U and Wilcoxon regression tests were used in the statistical analyses. Results The median age is 68 (59-76) years. Grade 2 acute GUS toxicities were observed in 59% of the patients, and there was no grade 3-4 toxicity. The average dose values were 5335 (4337-5995) cGy for the bladder, 7068 (6479-7873) cGy for the trigone and 7901 (7624-7995) cGy for the urethra, respectively. No significant relation was demonstrated between acute GUS toxicities and patient’s previous history (p>0.05).There was a tendency towards a statistically significant relationship between the trigone V55 (p= 0.07) and the V60, and a statistically significant association was found between the minimum trigone dose (p= 0.02) and V65 (p= 0.02).Due to the low number of patients and events, a cut-off value could not be identified in the ROC analysis. Conclusion The demonstration of a significant relationship between acute GUS toxicities and increasing trigone doses shows that this structure should be taken into consideration

Conclusion In our experience CK-SRT seem to be safe and reliable in the LPC. No severe toxicities were reported and the patients were very compliant. Careful patient selection is critical to achieve maximum effectiveness by CK SRT. More patients and longer follow up are necessary in order to evaluate the real advantage of SRT respect to standard fractionation in terms of overall survival, biochemical free survival and late toxicity. EP-1335 Hypofractionated versus conventional radiotherapy in intermediate- to high-risk prostate cancer W. Guo 1 , X.S. Gao 1 , X.B. Gu 1 , M.W. Ma 1 1 Peking University First Hospital, Department of Radiation Oncology, Beijing, China Purpose or Objective Prostate cancer is one of the most common cancers in the world, and the population of patients with intermediate- to high-risk localized prostate cancer (PCa) occupies a large proportion. The results of treatment after hypofractionated radiotherapy only have been reported from several small randomized trials. Therefore, we pooled the relevant data and conducted a meta-analysis to compare clinical outcomes of hypofractionated radiotherapy versus conventional radiotherapy in the treatment of intermediate- to high-risk localized PCa. Material and Methods Relevant studies were identified through searching PubMed, Embase and Web of Science databases till August, 2016. Hazard ratio (HR) or risk ratio (RR) with its corresponding 95% confidence interval (CI) was used as pooled statistics for all analyses. Results Six clinical cohorts were included with a total of 1621 intermediate- to high-risk localized PCa patients. The meta-analysis results showed that overall survival (HR=1.00, 95% CI: 0.85-1.17, p =0.980) and biochemical failure (RR=0.87, 95% CI: 0.68-1.12, p =0.274) were similar in two groups. The incidence of acute adverse gastrointestinal event (grade ≥ 2) was higher in the hypofractionated radiotherapy (RR=1.87, 95% CI: 1.21-