ESTRO 36 Abstract Book

S387 ESTRO 36 _______________________________________________________________________________________________

GU and GI symptoms are compared in Table 1. Only night voiding frequency ≥4 was statistically significantly higher in the CK group (14.7%) compared to the HDR group (10.0%).

respectively, and late GU grade ≥ 3 toxicity was 2.6% and 4.5% respectively. The incidence of GI and GU Grade 3 toxicity was 6% for each. At last follow-up visit there were no GI Grade ≥ 3 toxicities and 2 GU Grade 3 toxicities. There was no significant difference in late GI nor late GU toxicity between patients receiving pelvic doses ≤ 50 Gy and > 50 Gy. Five-year biochemical control was 77%, and at 7 years was 67%, with significantly more failures in the node-positive cohort. Biochemical failures occurred in 44 patients (35%) and 14 died from disease (11%). Overall survival was 92% at 5 years and 87% at 7 years and significantly lower in those with nodal metastases. Conclusion IG-IMRT with dose-escalation to both the pelvic lymph nodes and prostate/seminal vesicles results in similar late toxicity to standard dose pelvic irradiation using 2D/3D- conformal techniques. There was no significant difference in toxicity with pelvic doses > 50 Gy compared to ≤ 50 Gy. Our biochemical control rates were comparable to that reported in the dose-escalated randomized trials. Patients with nodal metastases at diagnosis had worse outcomes compared to those without nodal disease . PO-0737 elective pelvic radiotherapy in clinically node- negative prostate cancer: a long-term analysis F. Catucci 1 , C. Masciocchi 1 , A.R. Alitto 1 , M. Vernaleone 1 , G.C. Mattiucci 1 , V. Frascino 1 , V. Valentini 1 , G. Mantini 1 1 Università Cattolica del Sacro Cuore -Fondazione Policlinico A. Gemelli, Radiation Oncology Division- Gemelli-ART, Rome, Italy Purpose or Objective Whole pelvic radiotherapy(WPRT) remains highly controversial in prostate cancer. Although randomized trials failed to show a benefit for patients that received prophylactic irradiation(46-50 Gy) of pelvic lymph- nodes(PLN), elective WPRT could be considered in high- risk patients, based on validated nomograms. Aim of this long-term analysis is to update data about a retrospective analysis, that supported WPRT only for patients with a high risk of Limphonodal Involment(LNI), using as threshold 30%, assessed by Roach equation. Material and Methods Patients classified in high- and very high-risk groups(Stage T3 or T4 and/or GS 8-10 and/or PSA level>20 ng/mL)were analyzed. LNI risk was assessed through Roach equation.RT was performed mainly with 3D technique after 2000. Prone or supine immobilization were used respectively in WPRT and Prostate Only RT(PORT). CTVs were: CTV1 prostate(total dose 7020/1.8 cGy fx until 1999 and 73.8/1.8 cGy fx afterwards), CTV2 seminal vesicles plus CTV1(total dose 55.8/1.8 cGy fx for cT1-T3a and 64.8/1.8 cGy fx for cT3b-T4), CTV3 PLN, in WPRT(total dose 4500/180 cGy fx). PTVs derived from a common margin of 1 cm to corresponding CTV.Long-term androgen deprivation therapy(ADT) was prescribed.Toxicity was graded according to the CTC v4.03.Statistical analysis was performed using R statistical software 3.2.4. Results Among the 358 patients enrolled between 1994 and 2007, we selected 319 high-risk ones:20 treated until 1999, by 2D RT, and 299, treated from 2000, by 3D RT; 147 (46.1%) treated with WPRT and 172(53.9%) with PORT. Median age at diagnosis was 70 years for WPRT(range 42 – 80) and 72 years for PORT(range 56 – 83) group. The two groups were heterogeneous for age, with a statistically significant difference between them(p=0,0017).With a median follow-up of 128 months, there were no statistically significant differences between WPRT and PORT groups, in terms of surrogate outcomes. Only OS resulted in a statistically significant difference between WPRT and PORT group, probably due to the initial heterogeneity in age; also among patients younger than 70 years, there weren’t statistically significant differences between the

Conclusion Extreme hypofractionated radiotherapy, delivering 4 fractions of 9.5 Gy with either HDR-brachytherapy or SBRT, is well-tolerated and safe with comparable late toxicity as other treatment modalities for low and intermediate risk prostate cancer. Compared to HDR, SBRT resulted in a slightly increased grade 2 GU toxicity rate and can therefore be used as an alternative for patients not eligible for brachytherapy. PO-0736 Long term outcomes of IG-IMRT dose- escalation to pelvis and prostate for advanced prostate cancer H. Lieng 1 , T. Rosewall 1 , H. Jiang 2 , A. Berlin 1 , R. Bristow 1 , C. Catton 1 , P. Chung 1 , J. Helou 1 , P. Warde 1 , A. Bayley 1 1 Princess Margaret Cancer Centre, Department of Radiation Oncology- Radiation Medicine Program, Toronto, Canada 2 Princess Margaret Cancer Centre, Department of Biostatistics, Toronto, Canada Purpose or Objective To evaluate late toxicity and long-term biochemical control for men with high-risk or node-positive (N1) prostate cancer treated with image-guided IMRT (IG-IMRT) and dose escalation to both the pelvic lymph nodes and prostate/seminal vesicles. Material and Methods Between 2002 and 2009, men with high-risk or N1 prostate cancer received dose-escalated IG-IMRT to the pelvis and prostate on a phase II clinical trial. The planned prescription dose was 55.1 Gy in 29 fractions to the prostate/seminal vesicles (P/SV) and pelvic lymph nodes (PLN), with a sequential boost dose of 24.7 Gy in 13 fractions to P/SV. Dose reductions were mandated to meet organ at risk constraints. Late RTOG gastrointestinal (GI) and genitourinary (GU) toxicity scores were recorded at each visit and biochemical failure was defined using the Phoenix criteria. Probability of toxicity and biochemical control were estimated using cumulative incidence function. Overall survival was calculated using the Kaplan- Meier method. Difference between groups was evaluated by Gray’s test or log-rank test. Results 124 men received IG-IMRT to the prostate and pelvic lymph nodes. Median follow-up was 99.7 months (range 5 – 162 months). Men had T3-T4 (45%), N1 (13%), Gleason 8- 10 (52%) disease with median PSA 24 ng/mL. The median age was 68 years and 85% received at least 2 years of androgen deprivation therapy. 112 (82%) received the total prescription dose to P/SV, with 67 (54%) receiving the planned dose to PLN of 55.1 Gy, and 106 (85%) receiving at least 50 Gy to PLN. The 5- and 7-year cumulative incidence of late GI grade ≥ 2 was 16.3% and 17.3%, with cumulative incidence of late GU grade ≥ 2 toxicity of 8.3% and 13.1% respectively. Late GI grade ≥ 3 toxicity at 5 and 7 years was 4.9% and 5.8%