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Background: Endoscopic submucosal dissection (ESD) can be used as a less invasive treatment option for superficial esophageal cancer involving the muscularis mucosae (T1a-MM) or upper third of the submucosa (T1b-SM1). Additional treatment after ESD is needed to prevent lymph node metastasis. However, the efficacy of radiotherapy following ESD has not been well evaluated. Moreover, the clinical outcomes of patients with large mucosal defects of the esophagus who received radiotherapy after ESD have not been reported. This study aimed to clarify the efficacy of additional radiotherapy following ESD for esophageal squamous cell cancer involving T1a-MM or T1b-SM1.

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Results: With the1 min. irradiation, the neutron yield from brass is about a factor of 3 lower than that of W, and the decay of activities is about 10 times faster. For the second simulation, the neutron activity builds up slowly in brass, from about 7x10 3 Bq/cm 3 at the end of week one to a maximum of 10 4 Bq/cm 3 at the end of week 7. For W, the neutron activity builds up slowly from about 5.5x10 6 Bq/cm 3 at the end of week one, to about 9x10 6 Bq/cm 3 (0.24 mCi) at the end of week 5. The neutron activities at the beginning of the week (during irradiation) are due to nuclides with atomic numbers in the range Z = 8 -78. At the end of the week, the neutron activities are mostly due to nuclides in the range Z = 60-78, and a smaller contribution from nuclides in the range Z = 20-60. Conclusions: Our simulation showed that brass results in much lower neutron production than W. Although neutron activity slowly builds up in W, the activity is only about 0.24 mCi after 5 weeks at the surface of the metal. At the patient level, the activity will be smaller due to inverse square law. Our next step is to simulate a realistic treatment schedule with a commercial MLC to more accurately predict the neutron activities.Purpose/Objective(s): The purpose of this study is to clarify the incidence, the risk factors, and the dose-volume relationship of radiation induced rib fracture after hypofractionated stereotactic body radiation therapy (SBRT). consecutive patients treated with hypofractionated SBRT for primary or metastatic lung cancer were reviewed. The inclusion criteria were at least 3 months of follow-up by CT scan and no previous overlapped radiation exposure. Radiation induced rib fractures were defined as rib fractures located in the radiation field, detected by CT scan after treatment. The risk factors considered; age, gender, GTV diameter, chest wall -tumor distance were reviewed and each parameter was divided into two groups. Dose-volume histogram analysis was conducted on ribs received over 20 Gy at maximal point dose. The max dose and absolute volume received; $10 Gy, $20 Gy, $30 Gy and $40 Gy were determined for each ribs as the dosimetric parameters. The 3-and 5-year Kaplan-Meier (KM) estimates of rib fracture were calculated. Each risk factor was assessed by a log-rank test. The optimal cut off value for each dosimetric parameter was analyzed through the use of receiver-operating characteristic (ROC) curves. The area under the curve (AUC) values were also calculated. To estimate the cumulative risk of fracture, the ribs were divided into two groups according to the cutoff value and compared by log-rank test. S136 I. J. Radiation Oncology d Biology d Physics Volume 78, Number 3, Supplement, 2010 Results: From 129 patients, 409 ribs met the inclusion criteria. Median follow-up period was 19 months. Among the 129 patients, 26 patients (44 ribs) experienced radiation induced rib fractures. The KM estimates of rib fracture at 3 years and 5 years were 35.3%, 53.7%, respectively. As a risk factor, chest wall -tumor d...