ESTRO 38 Abstract book

S763 ESTRO 38

died of esophageal cancer. Grade 3 or worse non- hematological toxicities were within acceptable range. Conclusion Treatment results of radiation therapy for patients with superficial esophageal cancer mainly unfit for surgery were retrospectively analyzed. Adaptive RT-field setting prevented isolated regional recurrence in superficial esophageal cancer. EP-1402 Hypofractionated radiotherapy for patients with bulky unresectable biliary tract cancer W. Kong 1 , J. Yang 1 , J. Yan 1 , J. Liu 1 , Z. Xia 1 , S. Li 1 , Y. Qiu 2 , B. Liu 1 1 Drum Tower Hospital- Medical School of Nanjing University & Clinical Cancer Institute of Nanjing University, The Comprehensive Cancer Centre, Nanjing, China ; 2 Drum Tower Hospital- Medical School of Nanjing University & Clinical Cancer Institute of Nanjing University, Department of General Surgery, Nanjing, China Purpose or Objective The treatment options are limited for the patients with unresectable biliary tract cancer (BTC), especially after the failure of the first-line chemotherapy. Although target therapy and checkpoint inhibitor therapy have improved the prognosis of a variety of advanced cancers in recent years, it has not been successful in treating advanced BTC. Unresectable advanced biliary tract cancers are often accompanied by extensive invasion or regional lymph node metastasis, and conventional radiotherapy can only achieve palliative effects. This study was the first to use helical tomotherapy-based hypofractionated radiotherapy to treat patients with bulky locally advanced and unresectable BTC (excluded diffuse metastatic disease). Material and Methods In total, we retrospectively analyzed 23 patients with bulky unresectable BTC (tumor size>10cm) treated by tomotherapy-based hypofractionated radiotherapy at Drum Tower Hospital between Feb 2015 and Oct 2017. The irradiated sites covered primary tumors and areas of local invasion, including metastatic lymph nodes that were confined to the abdominal or retroperitoneal space. Cox regression modal and Kaplan-Meier analysis were used to analyze the associations between patients’ characteristics and overall survival (OS). Results The median total radiation dose was 54Gy (range 28-72Gy) and median biologically effective dose (BED) was 74.4Gy (range 37.8-115.2Gy). The median planning target volume (PTV) was 445.79cm 3 . Based on the various PTVs, patients received 2.4-6Gy/fraction with 8-28 fractions. After the radiotherapy, the local control rate was 65.2% and the median OS was 11.3 months (range 2.1-31.9 months). The most common cause of death was out-field failure and only three patients died of in-field failures. The longest survival was 31.9 months. BED ≥70Gy significantly improved OS, compared to BED ＜ 70Gy (16.8 months vs. 5.05 months) (hazard ratio [HR] 0.146, 95% confidence interval [CI] 0.028-0.762, P =0.022). No patients developed grade≥4 toxicities. Conclusion Helical tomotherapy-based hypofractionated radiotherapy was effective and well tolerated for patients with bulky unresectable BTC. The dose escalation with higher BED could improve the survival for such patients. This might be a treatment option for patients with locally advanced biliary tract cancer, which cannot obtain benefit from the first-line chemotherapy. EP-1403 Retrospective evaluation of usefulness of MR- guided adaptive radiotherapy of gastric MALT lymphoma K. Okuma 1 , H. Okamoto 1 , K. Iijima 1 , F. Nishioka 1 , T. Kashihara 1 , S. Shima 1 , M. Uematsu 1 , H. Igaki 1 , Y.

gastrectomy. Both IMRT and VMAT plans were generated on the Pinnacle treatment planning system and TOMO plans were generated using a helical tomotherapy system. Adjuvant radiotherapy was prescribed with a total radiation dose of 50.4 Gy in 28 fractions. Results In proximal SC, TOMO achieved a significantly lower dose for the heart, total kidney, left kidney, and liver than that of IMRT or VMAT ( p < 0.05). In middle/distal SC, lower total kidney mean dose and V20 were observed with TOMO compared with IMRT ( p = 0.010 and 0.011, respectively) and VMAT ( p = 0.049; p = 0.014). Conclusion For the adjuvant treatment of gastric cancer, TOMO not only provided superior dose sparing for total kidney, left kidney, and liver V30 in patients with proximal gastric cancer but also significantly lowered the heart dose in proximal SC when compared to IMRT or VMAT plan. EP-1401 Practice–based clinical outcome of definitive radiation therapy for superficial esophageal cancer T. Uno 1 , H. Kobayashi 1 , M. Watanabe-Nemoto 1 , R. Harada 1 , M. Saito 1 , A. Kanazawa 1 , Y. Iwai 1 , K. Murakami 2 , H. Matsubara 2 1 Chiba University Hospital, Department of Radiology, Chiba-City, Japan ; 2 Chiba University Hospital, Department of Esophageal-Gastro-Intestinal Surgery, Chiba-City, Japan Purpose or Objective To evaluate treatment patterns and clinical outcome of definitive radiation therapy for patients with T1b superficial esophageal cancer unfit for or refused definitive surgery in the Authorized Institute for Board Certified Esophageal Surgeon in Japan. Material and Methods Treatment chart of 51 patients (men/women: 44/7) with T1b superficial esophageal cancer treated with definitive radiation therapy between 2000 and 2017 were retrospectively reviewed. The median age was 77 years with a range of 52 to 88. The tumor length ranged from 2 to 15 cm (median, 5 cm). Thirty-eight patients did not have surgical candidate due to several reasons such as medical condition, high age, and preceding other cancer treatment. Thirteen patients including 5 with primary tumor located at the cervical esophagus refused surgery. All patients received external beam radiation therapy using linear accelerator with high-energy X-ray. The median total dose was 60 Gy. Field of radiation therapy was individualized considering patient and clinical factors such as age, performance status, primary tumor location and tumor length; local field with no lymph node prophylaxis was used in 11, long-I field in 17, long-T field in 18, and short-T field in 5. Every patient received computer-based adaptive 3D treatment. Seven patients underwent intracavitary brachytherapy using Ir-192 high- dose-rate remote after-loading system. Prescribed dose of brachytherapy was 10-12 Gy in 2 fractions for 5 mm submucosa. Concurrent chemotherapy (CDDP+5FU) was used for 32 patients. Results Eight patients had local recurrence and only 3 patients developed isolated regional recurrence outside the field of radiation therapy. At the time of data analysis, a total of 20 patients have died. Of those, however, esophageal cancer specific death was only 6 patients. Six patients had died of other cancer; HCC in 2, gastric cancer in2, tongue cancer in 1 and pancreatic cancer in 1. The 3- and 5-year cause-specific survival rates were 83% and 69%. Among clinical factors such as age, gender, primary site, tumor length, tumor depth, use of concurrent chemoradiation (CCRT), field of RT and initial response, only the use of CCRT significantly influenced overall survival (OAS at 3 year, 56% and 70%, p=0.01). Tumor location had marginal impact on OAS. None of 8 patients with Ce-Ut legion had