Abstract Book

S33

ESTRO 37

2 Oscar Lambret Comprehensive Cancer Center, Radiotherapy Department, Lille, France

concurrent weekly cisplatin. Twenty-two (15%) patients had FIGO stage I; 65 (44%) II; 42 (28%) III and 19 (13%) IVA. Forty-six (31%) patients had pelvic and/or inguinal lymph node metastases. Median age at time of diagnosis was 63 years (range 24-89). Median follow-up was 29 months (range 3-167). Most patients (78%) were treated with PDR and combined intracavitary plus interstitial brachytherapy (55%). The median volume of the CTV was 17,6 cm3 and the D90 was 80 Gy (52-110Gy). The median doses to the D2cc of the bladder, rectum, sigmoid and bowel were 64 Gy (7-130), 63,5 Gy (22-88), 48,6 Gy (0- 74) and 48,9 Gy (0-74), respectively. At 3 and 5 years, the local control rate was 84% and 82%, respectively, disease free survival was 69% and 65%, respectively and overall survival was 75% and 68%, respectively (Figure 1). Combined crude grade 3/4 bladder and bowel morbidity was 10,8% and grade 3/4 vaginal morbidity was 9,5%. Patients in the group with a T2-4 tumor that received a dose to the CTV of more than 80 Gy had a significant better local control than patients who received less than 80 Gy (Figure 2).

Purpose or Objective To determine the correlation between dose volume parameters of the bladder and trigone bladder and late urinary toxicity in locally advanced cervical cancer patients treated with pulsed-dose-rate brachytherapy (PDR BT). Material and Methods 298 consecutive patients with International Federation of Gynecology and Obstetrics (FIGO) stage IB to IVA cervical carcinoma treated with concurrent chemo-radiation therapy and PDR BT from 2004-2015 were included. Dosimetric evaluation (D0.1cm 3 , D2cm 3 , D2cm 3 /pulse, D2 cm 3 , D1cm 3 /pulse, D1cm 3 , D0.5cm 3 /pulse, D0.5 cm 3 , Dmax/pulse, Dmax, Dmean/pulse, Dmean) and volumetric parameters (cm 3 ) of the whole bladder and trigone bladder were analyzed. Trigone was delineated as the triangular structure between the internal urethral orifice caudally and the two ureteral orifices cranially. Cumulative doses (including external beam radiotherapy contribution) were analyzed according to International commission on Radiation Units and Measurements (ICRU) and converted into EQD2 (α/β=3Gy). These parameters were examined as potential predictors of late toxicity, which was classified using Common Terminology Criteria for Adverse (CTCAE) v.4.0. Grade 2 urinary toxicity was the criteria. Univariate and multivariate analyses were conducted. Results Median follow-up was 4.9 years (4.5-5.3). Survival rates without grade 2+ urinary toxicity at 3 and 5 years were 69.8% (95%CI: 67.0-72.6) and 63.8% (95%CI: 60.7-66.9), respectively; and were 84.2% (95%CI: 81.8 - 86.6) and 78.5% (95%CI: 75.5-81.5) for patients without local relapse. Mean bladder D 2cm3 was 68.5Gy (interquartile [IQ]: 62.8–73.0). Dmean of bladder trigone was 60Gy (IQ: 54.7-65). After univariate analysis for 237 patients without local relapse, D 2cm3 was strongly associated with probability of urinary toxicity, which increased when D 2cm3 >70Gy (p=0.006). The effect was still higher for higher thresholds (p<0.001 for D 2cm3 >75Gy or >80Gy). ICRU bladder (p=0.021), D 0.1cm3 (p=0.018) and D 2cm3 (p=0.006) were significant, and volume of the bladder (p=0.068) was borderline. Using a cut-off of 65Gy, the mean bladder trigone dose correlated with urinary toxicities (p=0.007). There was a strong association between dosimetric parameters of the whole bladder and trigone (p<0.0001). In multivariate analysis, two parameters were associated with late grade 2+ urinary toxicity: 1/ bladder D 2cm3 , whatever the cut-off: >70Gy (HR=1.917; 95%CI 1.044–3.519) >75Gy (HR=2.483; 95%CI 1.300–4.742) or >80Gy (HR=3.814; 95%CI 1.752–8.301); and 2/ Dmean of the bladder trigone, with a cut-off 65Gy (HR = 2.031; 95%CI 1.023 – 4.033). Conclusion In this analysis based on a homogeneous cohort of patients, significant relationships were shown between bladder and trigone dose/volume parameters and probability of urinary toxicity. An increased risk was seen for bladder D2cm 3 >70Gy, suggesting that bladder sensitivity is higher than previously believed. Further studies are needed to validate these findings. OC-0072 Risk factors for ureteral stricture after IGABT in cervical cancer: results from the EMBRACE studies L.U. Fokdal 1 , K. Tanderup 1 , R. Pötter 2 , K. Kirchheiner 2 , A. Sturdza 2 , C. Chargari 3 , I. Jürgenliemk-Schulz 4 , B. Segedin 5 , L.T. Tan 6 , P. Hoskin 7 , U. Mahantshetty 8 , K. Bruheim 9 , B. Rai 10 , C. Kirisits 2 , J.C. Lindegaard 1 1 Aarhus University Hospital, Department of Oncology, Aarhus C, Denmark 2 Medical University of Vienna, Department of Radiation Oncology, Vienna, Austria

Conclusion In this multicenter study on IGABT in vaginal cancer local control rates and severe bowel and bladder morbidity seem to compare favorably with published results from the radiographic era. To better understand the dose response and target volume relationships and to improve future outcomes in a (prospective) multicenter setting a common target concept for IGABT in vaginal cancer is essential. OC-0071 Bladder and bladder trigone dose/volume parameters: correlation with toxicity in cervical cancer E. Manea 1 , A. Escande 2 , S. Bockel 1 , F. Busato 1 , T. Kumar 1 , M. Laurans 1 , I. Dumas 1 , R. Mazeron Υ 1 , I. Lazarescu 1 , E. Deutsch 1 , C. Haie-Meder 1 , C. Chargari 1 1 Institut Gustave Roussy, Radiotherapy Department, Villejuif, France