Dosimetric Evaluation of a Set of Specifically Designed Grids for Treating Subcutaneous Superficial Tumor with 6 and 18 MeV Electron Beam External Radiotherapy

Background: Conventional electron beam radiotherapy used for treating superficial cancer tumors suffers from the disadvantage of low skin sparing effect. Furthermore, increasing electron energy for treating deeper-seated tumors leads to significant increase of skin dose. To overcome this, various grids are recommended for electron beam radiotherapy of subcutaneous tumors. However, appropriate grids are required to be designed for decreasing skin dose while delivering uniform high doses to deep-seated superficial tumors. Our goal was to design, examine and propose appropriate grid(s) for optimum electron beam radiotherapy of subcutaneous tumors with the best skin sparing with 6 and 18 MeV energies.Materials and Methods: Relevant dosimetric characteristics were determined and analyzed for five grids manufactured from dry lead having various cavity diameters (1.5, 2.0, 2.5, 3.0, 3.5 cm) and shielded areas (0.3, 0.4, 0.5, 0.6, 0.7 cm) among the cavities but the same fraction of cavity/open (68%) and shielded/closed (38%) areas under the grid plates. Isodose distributions and dose profiles resulted from the grids were investigated using EDR2 films and MATLAB software. Results: The grids with 2 and 2.5 cm diameter cavities and 0.4 and 0.5 cm shielded areas were the most appropriate grids for 6 and 18 MeV radiotherapy, respectively. With these grids, the 100% PDDs (percentage depth doses) located at 1.25 and 2.5 cm for an open filed (without the grids) were moved down to 1.87 and 5.4 cm for 6 and 18 MeV energies, respectively. Furthermore, the proposed grids provided the least peak to valley dose variations hence the most uniform doses delivered at their relevant depths of treatment. Conclusions: To decrease the skin dose in 6 and 18 MeV electron beam radiotherapy of superficial subcutaneous tumors, various home-made grids were designed and investigated. The most appropriate grids (having 2 and 2.5 cm cavity diameters for 6 and 18 MeV, respectively) provided the optimum dose delivery for superficial subcutaneous tumors locating around 1.5 and 5 cm depth for 6 and 18 MeV energies. Our comprehensive study provides reliable results that could be considered and developed more for a wider range of MeV electron grid therapies in routine clinical practices.

Endoscopic Images by a Single-Shot Multibox Detector for the Identification of Early Cancerous Lesions in the Esophagus: A Pilot Study

Diagnosis of early esophageal neoplasia, including dysplasia and superficial cancer, is a great challenge for endoscopists. Recently, the application of artificial intelligence (AI) using deep learning in the endoscopic field has made significant advancements in diagnosing gastrointestinal cancers. In the present study, we constructed a single-shot multibox detector using a convolutional neural network for diagnosing different histological grades of esophageal neoplasms and evaluated the diagnostic accuracy of this computer-aided system. A total of 936 endoscopic images were used as training images, and these images included 498 white-light imaging (WLI) and 438 narrow-band imaging (NBI) images. The esophageal neoplasms were divided into three classifications: squamous low-grade dysplasia, squamous high-grade dysplasia, and squamous cell carcinoma, based on pathological diagnosis. This AI system analyzed 264 test images in 10 s, and the sensitivity, specificity, and diagnostic accuracy of this system in detecting esophageal neoplasms were 96.2%, 70.4%, and 90.9%, respectively. The accuracy of this AI system in differentiating the histological grade of esophageal neoplasms was 92%. Our system showed better accuracy in diagnosing NBI (95%) than WLI (89%) images. Our results showed the great potential of AI systems in identifying esophageal neoplasms as well as differentiating histological grades.

Evaluation of miR-146a Urinary Level as a Marker for Recurrence of Superficial Bladder Cancer after Transurethral Resection of Bladder Tumor (TUR-BT)

Background: The most prevalent malignancy affect the urinary system is bladder cancer which exhibits a markedly high recurrence rate. The level of urinary microRNA-146a (miR-146a) was significantly higher in superficial bladder cancer patients, and were decreased to normal range after transurethral resection of the bladder tumor (TUR-BT). Its level was increased again if there is recurrence of the superficial bladder tumor diagnosed by follow up cystoscopy. miR-146 may be a clinically important marker for diagnosis and recurrence of superficial bladder cancer and is used instead of follow up operations as follow up cystoscopy for follow up of recurrence . Objective: our work aims to detect a simple, reliable and noninvasive diagnostic and surveillance methods for follow up of superficial bladder cancer. Methodology: The level of miR-146a in urine of 30 superficial bladder cancer patients was evaluated by quantitative reverse transcription polymerase chain reaction assay using voided urine samples before, after TUR-BT and after 3, 6,9,12 months of resection and compared with the result of follow up cystoscopy. Results: miR-146a was significantly increased in urine samples from patients with superficial cancer bladder than in those from the normal individuals (P <.000). Elevated urinary miR-146a levels in patients with bladder cancer were lowered to the normal level after TUR-BT and increased again in those who have tumor recurrence and remain in a normal level in those who have no recurrence after follow up for 3 ,6, 9,12 months after surgery(P=. 007, P=.000 respectively).Conclusion: Our study concluded that urinary miR-146a may be useful as a novel noninvasive diagnostic and follow up marker, anticancer agent or therapeutic target for superficial cancer bladder, also for increasing our knowledge of cancer biology.

PS02.222: CLINICAL CHARACTERISTICS AND MANAGEMENT OF GASTRIC TUBE CANCER AFTER ESOPHAGECTOMY

Background Gastric cancer is the second most common malignancy, overlapping with thoracic esophageal cancer (TEC). Among them, metachronous gastric tube cancers after TEC surgery have been increasing. The aims of this study were to examine the clinicopathological factors and treatment outcomes of gastric tube cancer (GTC) after TEC surgery. Methods Thirty-three GTCs in 30 cases after TEC treated between 1997 and 2016 were investigated retrospectively. Results Most cases were males. The median interval from TEC surgery to GTC occurrence was 68.1 months (6–190 months). Almost 2/3 lesions occurred in the lower third of the gastric tube (21/33); 29 lesions (in 26 cases) were superficial cancers, and 4 lesions were advanced cancers. Twenty-two lesions of superficial cancer were differentiated type, and the remaining seven lesions were undifferentiated type. Treatment for superficial cancer had previously been performed with partial gastric tube resection (10 lesions), and the number of cases undergoing endoscopic submucosal dissection (ESD) had increased recently (19 lesions). Most cases with superficial cancer survived without relapse. Four lesions of advanced cancer were found after a relatively long interval following TEC surgery. Most lesions of advanced cancer were scirrhous, undifferentiated type, and they died due to GTC. Conclusion GTCs may occur late in the postoperative course following TEC surgery. If they are discovered at an early stage, these lesions can be cured with ESD. Long-term periodic endoscopic examinations after TEC surgery are important. Disclosure All authors have declared no conflicts of interest.