Long-term survival outcome of multi-institutional prospective phase II trial of conversion surgery: CCOG1403.

380 Background: From the result of CONVO-GC-1, safety and efficacy of conversion surgery are shown. But there are few prospective studies about conversion surgery. We conducted multi-institutional prospective study of conversion surgery (CCOG1403). Methods: The patients (pts) with gastric cancer, who were initially regarded as non-curable and curably resectable after at least one course of chemotherapy, were enrolled. After diagnostic laparoscopy or laparotomy, pts were performed gastrectomy in case of curably resectable. The primary endpoint was 3-year survival from the start of first line chemotherapy. The planned sample size was 30, with one-sided alpha of 5%, power of 90%, expected 3-year survival rate of 27%, and threshold of 7%. Secondary endpoints were 5-year survival from the start of first line chemotherapy, the proportion of R0 resection, 3-year survival from the conversion surgery, pathological response, and adverse events. This study was registered at the University Hospital Medical Information Network Clinical Trials Registry as UMIN000014251. Results: From April 2014 to March 2019, 30 pts were enrolled from 7 institutions. The mean age was 66.7. Non-curable factors were PER(11), LYM(9), HEP(6), T(4), CY(1), PUL(1), BRA(1), and other(1), respectively. Four pts had more than one non-curable factors. The categories of Yoshida’s classification were Cat.1(3), Cat.2(16), Cat.3(8), and Cat.4(2). Regimen of chemotherapy were SOX (11), SP (8), XP+HER (8), PTX ip containing regimen (6), and others (12). Clinical responses of preoperative chemotherapy were PR in 24 and SD in 6. Operative procedures were TG (18), DG (7), and PG (1). Median operative time was 278.5min. and median blood loss was 417.5ml. Twenty-four (80%) pts achieved R0 resection. Five pts suffered >= C-D Grade III postoperative complication but all pts recovered. The pathological finding revealed major response, defined as disappearance more than two third of the primary tumor, in 26.7% (8/30) pts. Twenty-seven (90%) pts received postoperative chemotherapy. Among 24 pts with R0 resection, 16 pts experienced recurrence in PER(5), LYM(4), HEP(4), PUL(3), BRA(1), and others(4). In 30 pts accrued, 19 (66.3% 43.9-80.1), 16 (55.3% 34.3-71.7) survived more than 3 years from the start of first line chemotherapy and the conversion surgery, respectively. Conclusions: Conversion surgery is effective and worth for testing in the following randomized trial. Clinical trial information: UMIN000014251 .