Sequential Paclitaxel Followed by Tegafur and Uracil (UFT) or S-1 Versus UFT or S-1 Monotherapy As Adjuvant Chemotherapy for T4a/b Gastric Cancer (SAMIT): a Phase 3 Factorial Randomised Controlled Trial

Background: The prognosis for locally advanced gastric cancer is poor despite advances in adjuvant chemotherapy. We did the Stomach cancer Adjuvant Multi-Institutional group Trial (SAMIT) to assess the superiority of sequential treatment (paclitaxel then tegafur and uracil [UFT] or paclitaxel then S-1) compared with monotherapy (UFT or S-1) and also the non-inferiority of UFT compared with S-1.

Methods: We did this randomised phase 3 trial with a two-by-two factorial design at 230 hospitals in Japan. We enrolled patients aged 20-80 years with T4a or T4b gastric cancer, who had had D2 dissection and a ECOG performance score of 0-1. Patients were randomly assigned to one of four treatment groups with minimisation for tumour size, lymph node metastasis, and study site. Patients received UFT only (267 mg/m(2) per day), S-1 only (80 mg/m(2) per day) for 14 days, with a 7-day rest period or three courses of intermittent weekly paclitaxel (80 mg/m(2)) followed by either UFT, or S-1. Treatment lasted 48 weeks in monotherapy groups and 49 weeks in the sequential treatment groups. The primary endpoint was disease-free survival assessed by intention to treat. We assessed whether UFT was non-inferior to S-1 with a non-inferiority margin of 1·33. This trial was registered at UMIN Clinical Trials Registry, number C000000082.

Findings: We randomly assigned 1495 patients between Aug 3, 2004, and Sept 29, 2009. 374 patients were assigned to receive UFT alone, 374 to receive S-1 alone, 374 to received paclitaxel then UFT, and 373 to receive paclitaxel then S-1. We included 1433 patients in the primary analysis after at least 3 years of follow-up (359, 364, 355, and 355 in each group respectively). Protocol treatment was completed by 215 (60%) patients in the UFT group, 224 (62%) in the S-1 group, 242 (68%) in the paclitaxel then UFT group, and 250 (70%) in the paclitaxel then S-1 group. 3-year disease-free survival for monotherapy was 54·0% (95% CI 50·2-57·6) and that of sequential treatment was 57·2% (53·4-60·8; hazard ratio [HR] 0·92, 95% CI 0·80-1·07, p=0·273). 3-year disease-free survival for the UFT group was 53·0% (95% CI 49·2-56·6) and that of the S-1 group was 58·2% (54·4-61·8; HR 0·81, 95% CI 0·70-0·93, p=0·0048; pnon-inferiority=0·151). The most common grade 3-4 haematological adverse event was neutropenia (41 [11%] of 359 patients in the UFT group, 48 [13%] of 363 in the S-1 group, 46 [13%] of 355 in the paclitaxel then UFT group, and 83 [23%] of 356 in the paclitaxel then S-1 group). The most common grade 3-4 non-haematological adverse event was anorexia (21 [6%], 24 [7%], seven [2%], and 18 [5%], respectively).

Interpretation: Sequential treatment did not improve disease-free survival, and UFT was not non-inferior to S-1 (and S-1 was superior to UFT), therefore S-1 monotherapy should remain the standard treatment for locally advanced gastric cancer in Japan.

Funding: Epidemiological and Clinical Research Information Network.