ESTRO 36 Abstract Book

S379 ESTRO 36 _______________________________________________________________________________________________

Purpose or Objective Pelvic insufficiency fractures (PIF) are frequently reported late effect in women who undergo pelvic radiation therapy (RT) for cervical and uterine carcinomas, ranging from 5- 15%, though the majority of these are asymptomatic. Other known risk factors include age, pre-existing osteoporosis, and post-menopausal status. Because the majority of PIF are clinically insignificant, we sought to determine predictors of the development of symptomatic PIF in women undergoing pelvic RT. Material and Methods This is a retrospective review of women treated between 1999 and 2013 for uterine or cervical cancer at single institution. All patients received external beam RT with either 3DCRT or IMRT technique to at least 45Gy followed by high dose-rate Intracavitary brachytherapy. Time to symptomatic PIF was calculated as the time from completion of RT to diagnostic imaging demonstrating fracture. Independent t-test and Chi-squared analysis were utilized to determine association between demographic and dosimetric variables and symptomatic PIF. Results 253 consecutive patients were identified, 77 (30.4%) of whom had RT plans available for review. The median patient age at diagnosis was 63. The external beam RT dose was 45.0-50. The average mean sacral dose was 37.8Gy (range: 27-44.7Gy). Seven patients (9.1%) were diagnosed with symptomatic PIF at a median time from RT of 23.6 months (range: 7-98 months). Median sacral V20 and V30 were 99.7% and 83.7%, respectively. Sacral V20 was significantly associated with symptomatic PIF (p=.008) and V30 trended towards significance (p=.054). Sacral V30 ≥ 83.7% predicted for the risk of symptomatic PIF (p=.05). Conclusion This is the first study to correlate symptomatic pelvic insufficiency fracture to dosimetric parameters involved in pelvic RT in women. Limiting sacral V30 < 83.7% is recommended and further study is warranted. We will further validate this data in our larger dataset given the small number of events. PO-0723 Phase II study with FFF linac-based SBRT in 5 fractions for localized prostate cancer F. Alongi 1 , U. Tebano 1 , S. Fersino 1 , A. Fiorentino 1 , R. Mazzola 1 , N. Giaj-Levra 1 , F. Ricchetti 1 , D. Aiello 1 , G. Sicignano 1 , S. Naccarato 1 , R. Ruggieri 1 1 Sacro Cuore Don Calabria Cancer Care Center, Division of Radiation Oncology, Negrar, Italy Purpose or Objective SBRT is recently considered a potential treatment option in selected prostate cancer (PC) patients. 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. Aim of the present phase-II study is to evaluate the feasibility, side effects and biochemical control of FFF SBRT delivered in 5 consecutive days in a cohort of localized PC patients. 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- 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. Poster: Clinical track: Prostate

The SBRT-schedule was 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 At the time of the analysis, forty-two patients were recruited in the protocol and treated. Median age was 74 years (63-80), Median follow-up was 19 months (range: 12- 31). According to risk-category, 31/42 patients were low- risk and 11/42 were intermediate risk. Median initial PSA was 6.1 ng/ml (range, 3.4-12.8 ng/ml). Median Gleason score was 6 (6-7). IPSS pre-SBRT was registered for all patients, with a median value of 4 (range, 0 - 10). All patients completed the treatment as planned. Acute genitourinary toxicity was: G0 29/42 (70%), G1 7/42 (17%), G2 6/42 (13%). Acute gastrointestinal toxicity was: G0 36/42 (86%), G1 4/42 (9%), G2 2/42 (5%). No acute toxicities > G3 were recorded. At the time of the analysis late GU and GI toxicities were: GU-G0 33/42 (78%), GU-G1 7/42 (17%), GU-G2 1/42 (2%), GU-G3 1/42 (2%); GI-G0 39/42 (93%), GI-G1 3/42 (7%) and the median value of IPSS was 4.5 (range, 0 - 20). To date, biochemical control was 100%. Conclusion The present FFF SBRT phase-II study for low-intermediate PC delivered in 5 consecutive days showed to be feasible and well tolerated as well as other series with the same technique and fractionation delivered every other day (Alongi et al Radiation Oncology 2013). Longer follow-up is needed to assess late toxicity profile and clinical outcomes. PO-0724 Moderate hypofractionated radiotherapy in prostate cancer: a meta-analysis from randomized trials Z. Yin 1 , Z. Yuan 2 , J. You 2 1 Tianjin Medical University Cancer Institute & Hospital, Radiotherapy, tianjin, China 2 Tianjin Medical University Cancer Institute and Hospital, Department of radiotherapy, Tianjin, China Purpose or Objective Conventional radiotherapy (C-RT) with dose more than 75.6Gy was the current standard treatment for patients with localized prostate cancer. While prostate cancer’s biological characteristics, lowα/βratio, makes it more radiosensitive to hypo-fractionation. To compare the efficacy and late toxicity of moderate (2.5-3.4Gy) hypo- fractionated radiotherapy (H-RT) in localized prostate cancer with conventional fractionated RT (C-RT), we performed a systematic review and meta-analysis of published randomized trials. Material and Methods Systematic search on published RCTs in English according to Cochrane review guidelines in database of Pubmed, Embase, Cochrane, web of science, and Wiley Online Library were carried out. Outcome of interest was biochemical or clinical disease failure (BCDF), biochemical failure (BF), overall survival (OS) and late toxicities Results 6 of 341 studies fulfilled inclusions with 6931 patients. There was no significant difference in BCDF between H-RT and C-RT (RR=0.94, 95% CI: 0.83-1.06, p =0.31), with a moderate heterogeneity (Chi 2 =6.23; df= 4[P=0.18]; I 2 =36%). We grouped them into dose-escalated H-RT and no dose-escalated H-RT, dose-escalated H-RT significantly improved BCDF compared with C-RT (RR=0.86, 95%CI: 0.74-0.99, p =0.04). Patients who received H-RT showed a lower BF (RR=0.78, 95% CI: 0.63-0.97, p =0.03), without heterogeneity (Chi 2 =0.86; df=2[P=0.65]; I 2 =0%). There was no significant difference in overall survival (RR=0.89, 95% CI: 0.76-1.03, p =0.12) between H-RT and C-RT, also no heterogeneity noted (Chi 2 =3.53; df=4[P=0.47]; I 2 =0%). As