Randomized phase III trial to evaluate omentum preserving gastrectomy for patients with resectable advanced gastric cancer: JCOG1711 (ROAD-GC).

TPS4646 Background: Standard surgery for resectable advanced gastric cancer is D2 (standardized extended lymph node dissection) gastrectomy with omentectomy. The reason why omentectomy has been performed is as follows; (1) principal surgery for gastrointestinal cancers is en-block resection of mesothelium including regional lymph nodes. Omentum is a part of the mesothelium of the stomach. (2) Cancer cells implanted into the peritoneal cavity aggregated in the milky-spot of the omentum and formed peritoneal dissemination in an animal model. (3) By special staining, micrometastasis detected in the omentum. There is some arguments for this theory. (1) no prospective study showed survival benefit of omentectomy as compared with omentum preservation. (2) anatomically, milky-spot is found not only in the omentum but also in other mesothelium or Douglas pouch. (3) JCOG1001 phase III study showed no survival benefit of bursectomy against non-bursectomy although bursa is a part of mesothelium of the stomach. (4) Anti-immunity is accelerated by antigen presentation by macrophage in the milky-spot of the omentum. Preservation of the omentum may have several benefits; (1) decrease in blood loss and operation time, (2) preservation of physical function by omentum such as reaction to peritonitis and prevention of adhesion, and (3) overcoming difficulties in laparoscopic omentectomy and avoidance of organ injury during surgery. Methods: The study is multicenter randomized phase III trial designed to confirm non-inferiority of omentum preservation to omentectomy for resectable advanced gastric cancer. Patients aged 20-79 years, histologically proven gastric adenocarcinoma, clinical subserosal/serosal invasion, and expected R0 (curative) resection are randomly assigned (1:1) during surgery to either omentum preservation or omentectomy. Total or distal gastrectomy with D2 dissection is performed in both arms. Laparoscopic gastrectomy is not allowed. Intraoperative photographs of the dissected field are centrally reviewed for all patients for quality control. The primary endpoint is relapse-free survival (RFS) and the secondary endpoints are overall survival, blood loss, operation time, and adverse events. Sample size was set at 1050 considering expected 3-year RFS of 77% in both arms with non-inferiority margin of 5%, one-sided alpha of 5%, and power of 80%. Planned accrual and follow up period are 6.5 years and 3 years respectively. The trial was activated in March 2019, and 177 patients are enrolled as of January 2020. Clinical trial information: UMIN000036253 .

X-Ray Investigations on Rubber

During some earlier x-ray investigations on cre^pe rubber, it was observed that the originally translucent sample became more and more milky at the spot where the x-rays passed the material. The sample was the same as described in an earlier paper. This rubber gave a distinct x-ray pattern during the first exposure, but, although the lines did not change their position, they became increasingly sharper with each exposure; simultaneously the opaqueness of the milky spot increased. The increase of sharpness of the originally broad lines represents, of course, increase in particle size; but evidently also the increasing cloudiness of the cre^pe rubber shows progressing crystallization.