ESTRO 36 Abstract Book

S514 ESTRO 36 2017 _______________________________________________________________________________________________

applicators were inserted, cone beam computed tomography (CT) images were obtained. Rectal gas was observed in 11 brachytherapy fractions from 8 patients. After draining rectal gas with a Nelaton catheter, cone beam CT images were obtained again. Brachytherapy was prescribed to point A using standard two-dimensional dosimetry and planning. To quantify the dose delivered to the rectum and urinary bladder, three-dimensional dose distributions were calculated using the images from before and after draining rectal gas. The dose to the rectum and urinary bladder was evaluated based on dose- volume histograms. The influence of the volume of discharging rectal gas (pre-draining rectal volume – post- draining rectal volume) on the rectal dose was investigated. The minimum doses to the maximum exposed 0.1, 1 and 2 cc (D 0.1cc , D 1cc and D 2cc ) volumes were evaluated using the dose from point A. Statistical analyses were conducted using the paired t-test and a linear regression model. Results The mean rectal dose after draining rectal gas was significantly lower than that before draining. The rectal doses (D 0.1cc , D 1cc and D 2cc ) relative to point A at post- draining vs. pre-draining were as follows: 106.9% vs. 121.2%, 88.3% vs. 98.6% and 81.5% vs. 90.9%, respectively (p<0.05). The mean urinary bladder dose was not significantly different after draining rectal gas from before. The urinary bladder doses (D 0.1cc , D 1cc and D 2cc ) relative to point A at post-draining vs. pre-draining were as follows: 136.0% vs. 133.2%, 112.3% vs. 111.8% and 103.3% vs. 102.4%, respectively. The volume of discharging rectal gas slightly correlated with the rectal dose at D 0.1cc (R2=0.45); however, no significant correlation was found for D 1cc or D 2cc (R2=0.10 and -0.01, respectively). Conclusion Our data suggested that draining rectal gas is useful for reducing the rectal dose in high-dose-rate brachytherapy for gynecological cancer. PO-0937 HDR image-guided interstitial brachytherapy for postoperative local recurrent uterine cancer K. Yoshida 1 , H. Yamazaki 2 , T. Takenaka 2 , T. Kotsuma 3 , K. Masui 2 , T. Komori 1 , T. Shimbo 1 , N. Yoshikawa 1 , H. Yoshioka 1 , Y. Uesugi 4 , T. Hamada 1 , M. Nakata 1 , H. Matsutani 1 , M.M. Ueda 3 , Y. Tsujimoto 3 , E. Tanaka 3 , Y. Narumi 1 1 Osaka Medical College, Radiology, Takatsuki, Japan 2 Kyoto Prefectural University of Medicine, Radiology, Kyoto, Japan 3 National Hospital Organization Osaka National Hospital, Radiation Oncology, Osaka, Japan 4 Kansai University of Welfare Sciences, Rehabilitation Sciences, Kashiwara, Japan Purpose or Objective In order to evaluate the usefulness of high-dose-rate (HDR) image-guided interstitial brachytherapy (ISBT) for postoperative local recurrent uterine cancer, we analyzed We investigated 48 patients treated with HDR-ISBT at National Hospital Organization Osaka National Hospital and Osaka Medical College between May 2003 and January 2014. All patients received radical surgery and 10 patients also received post-operative radiotherapy as previous treatments. Histologic finding was squamous cell carcinoma (SCC), endometrioid adenocarcinoma (AD), mucinous adenocarcinoma (MAD) and the others (serous/adenosquamous/endocrine/undifferentiated) for 20, 17, 5 and 6 patients. The median maximum tumor diameter was 25 mm (range; 5-79 mm). In 38 patients who had non-irradiation history, 23 patients also received external beam radiotherapy (EBRT). The median ISBT doses were 54 Gy in 9 fractions as monotherapy and 30 Gy our clinical experience. Material and Methods

in 5 fractions as combination of EBRT. In 10 patients who had irradiation history, lower doses (36 to 48 Gy in 6 to 8 fractions) were selected. We implanted 7–16 (median, 13) applicators under transrectal ultrasonography guidance. We used free-hand implantation with ambulatory technique for later 42 patients. Magnetic resonance imaging (MRI)-assisted image-based treatment planning was also performed. Clinical target volumes (CTV) were the gloss tumor volume with or without 10 mm of vaginal margin for patients with or without non-irradiation The median follow-up time was 41 months (range; 4-115 months). The median D90(CTV)s were 91.3 Gy and 75.6 Gy for patients with or without non-irradiation history. The 4- year local control and overall survival rates were 78% and 67% for all patients. The 4-year local control rates were 83% and 60% for patients with or without non-irradiation history (p=0.02). Tumor diameter, primary site and histology were not significant prognostic factors of local control. The 4-year overall survival rates were 73, 65, 100 and 20% for SCC, AD, MAD and the others (P=0.06). The D90(CTV)s were 93.5±24.3 Gy and 81.4±9.2 Gy for local control and failure patients (p=0.1). Grade ≥3 late complications occurred in 11 patients (23%). Ileus was only observed for patients receiving EBRT. Conclusion Our treatment result of image-guided HDR-ISBT showed good local control result. However, previous irradiation history was a worse prognostic factor of local control. Dose-volume histogram seems to be useful for dose prescription. PO-0938 Should we use point A dose for image-guided adaptive brachytherapy reporting in cervix cancer? R. Mazeron 1 , I. Dumas 2 , A. Escande 1 , W. Bacorro 1 , R. Sun 1 , C. Haie-Meder 1 , C. Chargari 1 1 Institut Gustave Roussy, Radiation Oncology, Villejuif, France 2 Institut Gustave Roussy, Medical Physics, Villejuif, France Purpose or Objective The recent ICRU report 89 recommends continuing the reporting of point A dose in the era of Image-guided adaptive brachytherapy (IGABT). The study aim was to evaluate the interest of such recommendation by testing the value of point A as a surrogate of volumetric dosimetric parameters and as a predicting factor of local control. Material and Methods The dosimetric data from patients treated with a combination of chemoradiation and intracavitory image- guided adaptive brachytherapy were confronted to their outcomes. Prescribing followed the GEC-ESTRO recommendations. Point A was used for reporting, without specific planning aim. All doses were converted in 2-Gy equivalent, summing brachytherapy and EBRT doses. The relationships between the D 90 CTV HR and CTV IR and point A doses were studied. Dose-effect relationships based on the probit model and log-rank tests were assessed using the different dosimetric parameters. Results Two hundred and twelve patients were included with a median follow-up of 53.0 months. MRI guidance was used in 89.6% of the cases. A total of 28 local relapses were reported resulting in a local control rate of 86.6% at 3 years. Mean D 90 CTV HR , D 90 CTV IR and point A doses were respectively: 79.7±10.4 Gy, 67.4±5.8 Gy and 66.4±5.6 Gy. The mean D 90 CTV HR and CTV IR were significantly different from the mean point A dose (p=p<0.0001, and 0.022 respectively). Both D 90 CTV were independent from point A doses, even in bulky (width >5cm) tumors at diagnosis or in large CTV HR lesions (≥ 30cm 3 ) Whereas significant relationships between the probability of achieving local history. Results