A phase 1b multicenter study of TAS-102 in combination with irinotecan in patients with advanced recurrent or unresectable gastric and gastroesophageal adenocarcinoma after at least one line of treatment with a fluoropyrimidine and platinum-containing regimen

TAS-102 is approved for treatment of refractory metastatic gastroesophageal carcinoma (mGEC). This study sought to determine whether the combination of TAS-102 with irinotecan (TASIRI) was safe and effective in previously treated mGEC. This was a single-arm phase 1b study for patients (pts) with mGEC previously treated with at least one line of fluoropyrimidine and platinum-containing regimen. TAS-102 was given at 25 mg/m² twice daily on days 1 to 5 with irinotecan 180 mg/m² on day 1 of a 14-day cycle. The primary endpoint was progression-free survival at 6 months ≥ 35% (PFS-6). 20 Pts were enrolled. The study met its primary endpoint. PFS-6 is 40% (95% CI 19.3-60.0). Median PFS and overall survival are 5.3 months and not reached, respectively. 17 of 20 pts had measurable disease by RECIST criteria. Of the 17, 13 had stable disease and 4 had progressive disease as best response (8 pts had tumor shrinkage < 30%). The disease control rate was 75%. In exploratory analyses, mutations in homologous recombination deficiency genes were associated with inferior PFS (P < 0.03). The most common any grade (G) treatment-related adverse events (TRAE) were nausea (n = 14, 70%), diarrhea (n = 9, 45%), and fatigue (n = 8, 40%). G3-4 TRAE in > 5% of pts were anemia (20%) and neutropenia (10%). 2 serious TRAE were reported: G4 febrile neutropenia (n = 1) and G3 hypotension (n = 1). There was no G5 TRAE. The combination of TASIRI showed encouraging clinical activity with a meaningful improvement in PFS-6 compared to historic controls.