ESTRO 36 Abstract Book

S669 ESTRO 36 2017 _______________________________________________________________________________________________

EP-1256 Local ablative radiotherapy for liver metastasis: factors affecting local control and survival C. Petersen 1 , T. Gauer 1 , T. Frenzel 1 , M. Todorovic 1 , A. Krüll 1 , M. Blaschczyk 1 1 University Medical Center Hamburg - Eppendorf UKE, Department of Radiation Oncology, Hamburg, Germany Purpose or Objective The liver is a common site of metastases from most common solid malignancies. Currently available systemic treatment regimens, result in transient to long-term disease control, raising the question of further local management. Secondary resection and thermo-ablation may contribute to long-term survival or allow at least a relevant chemotherapy-free interval. These approaches are often limited. With stereotactic body radiotherapy metastases can be treated with high efficiency in only a few sessions. Here we evaluate the feasibility of high-dose stereotactic body radiation therapy for liver metastases in patients not eligible for surgery focussing on colorectal cancer patients. Material and Methods Between July 2012 and December 2015, 33 patients with 56 liver metastases (range 1-4) were treated with SBRT. Primary tumor mostly consists of colorectal cancer (59%) and others (lung-, breast-, pancreatic cancer). Median time between diagnosis of liver metastases and SBRT was 11 months (range 0-57 months). To receive precise information about target localization, 3 gold fiducial markers were implanted in 30 out of 56 lesions (54%). To analyze respiratory tumor motion, 4D-CT scans were performed for all patients. Gross tumor volume contours of 10 breathing cycles were transferred to the average CT of the CD-CT data, forming the internal target volume (ITV). Planning target volume was obtained by adding a 4 mm margin. SBRT was delivered in VMAT technique using Varian TrueBeam linear accelerator. Most common fractionation schedule was 5 x 11 Gy (90% isodose covering the PTV). Results The median follow-up for all patients was 13 months. The overall local control rate for all 56 metastases was 86% with a total of 7 failures. In univariate analysis, the implantation of fiducial markers was predictive for local control (p=0.029). During follow up period, tumor progression developed in 28 cases (83%). In 13 cases new intrahepatic lesions occurred (47%), in 10 cases extra hepatic lesions (36%) and in 5 cases intra- and extra hepatic lesions (18%). Overall survival rate was 58%, median overall survival was 21 months. Univariate analysis showed statistical significance for OS concerning histology (colorectal vs. other) and gross tumor volume ( 20 ccm). Conclusion Liver SBRT is effective and yielded good local control. The SBRT procedure is a valid option for patients with oligometastatic disease and should be considered as an alternative to surgical treatment or other local ablative techniques.

In this investigation on patients treated for upper GI cancer, we recommend that V35.6 Liver (relative) should be held to < 22% in order to get upper GI toxicity grade ≥2 probability below 15%. Further investigations should be done in order to observe significant dosimetric evaluation in patients with grade≥3 toxicity. EP-1255 Early clinical results for esophageal brachytherapy using a novel multi-balloon HDR applicator A.S. Taggar 1 , G.N. Cohen 1 , P.J. Brady 1 , J.J. Cuaron 1 , A. Wu 1 1 Memorial Sloan Kettering Cancer Center, Radiation Oncology, New York, USA Purpose or Objective Management of superficial primary and locally recurrent esophageal cancer (EC) in medically inoperable patients is complex. Endoluminal high-dose-rate (HDR) brachytherapy (BT) has shown mixed results in terms of toxicity and local control (LC). In this study, we assessed the outcomes and toxicities in a set of patients treated in a consistent fashion with a novel multi-balloon HDR applicator (E-app) using CT-based planning. Material and Methods Five patients were treated with the E-app between November 2015 and August 2016 in a single institution. Their records were reviewed retrospectively under institutional ethics board approval. All patients were treated with HDR brachytherapy using the E-app and 3D CT-based treatment planning, and received a total of 15 Gy in 3 weekly fractions prescribed to tumor volume. All treatments were completed as planned. Four patients had distal esophagus/GE junction tumors, and one patient had mid-thoracic tumor. For one patient who presented with squamous cell (SC) and another with and neuro-endocrine (NE) histology, BT was the primary treatment. Three patients had adenocarcinoma histology and were previously treated with primary chemo/radiotherapy (CRT); two had residual disease after primary CRT and one presented with recurrence 8 years after initial treatment with CRT. Two patients with residual disease received concurrent Capecitabine, whereas all others were treated with BT only. Results Patients’ median (range) age and KPS at the time of BT were 76.6 years (66.0–87.6) and 80 (40–90), respectively. Median length of treatment was 7.0 cm (5.5–9.0 cm). Median dose to the hottest 0.3cc within defined esophageal target volume (D 0.3cc ) was 34.5 Gy (31.8–36.6 Gy). D 0.3cc and V 100 of esophagus outside target volume were 14.7 Gy (9.1–21.9 Gy) and 0.8 cc (0.0–3.6 cc), respectively. Median follow-up from BT was 6.1 months (1.7–7.3 months). Observed toxicities included dysphagia (2 patients, grade 1 and grade 2), esophagitis (1 patient, grade 1) stenosis (1 patient, grade 1) and asymptomatic necrosis within the target area (1 patient, prior treatment with 50.4 Gy + FOLFOX chemotherapy); no grade 3 toxicity was observed. Repeat biopsy at 3 months’ post BT was done in 3 out of 5 patients: 2 (patients with SC and NE histology) had no evidence of disease and one had persistent disease. One patient developed metastatic disease and died without endoscopic assessment or biopsy after BT. Conclusion This is the first report of clinical outcomes using a novel multi-balloon HDR brachytherapy applicator (E-App). The E-App appears to provide a safe and effective method of delivering high doses of radiation to localized esophageal cancers. We observed low rate of toxicity with short follow-up and promising clinical and pathological responses in the settings of recurrent and residual disease.

Electronic Poster: Clinical track: Lower GI (colon, rectum, anus)

EP-1257 A look at pre-operative MRI accuracy at predicting rectal cancer staging post chemoradiotherapy K. Nugent 1 , R. McDermott 1 , M. Higgins 1 , B. O'Neill 1 1 St Lukes Radiation Network, Radiation Oncology, Dublin, Ireland Purpose or Objective Neoadjuvant chemoradiotherpy (CRT) has become standard in the treatment of rectal cancer patients with