RAINBOW: A global, phase III, randomized, double-blind study of ramucirumab plus paclitaxel versus placebo plus paclitaxel in the treatment of metastatic gastroesophageal junction (GEJ) and gastric adenocarcinoma following disease progression on first-line platinum- and fluoropyrimidine-containing combination therapy rainbow IMCL CP12-0922 (I4T-IE-JVBE).

LBA7 Background: RAM is a human IgG1 monoclonal antibody VEGF-receptor 2 antagonist. We conducted a global, placebo-controlled, double-blind, phase III trial to evaluate the efficacy and safety of PTX +/- RAM in patients with metastatic GEJ or gastric adenocarcinoma who had disease progression on or within 4 months after first-line platinum- and fluoropyrimidine-based combination therapy. Methods: Pts received RAM (8 mg/kg IV q2w) or placebo (PL) plus PTX (80 mg/m 2 d1, 8, 15 of a 4 week cycle) until disease progression, unacceptable toxicity, or death. Eligible pts had ECOG PS ≤ 1; and adequate organ function. The primary endpoint was overall survival (OS). Secondary endpoints included progression-free survival (PFS), objective response rate (ORR), time to progression (TTP), and safety. Results: From Dec 2010 to Sep 2012, 665 pts were randomized (RAM+PTX: 330; PTX: 335). Baseline characteristics were generally balanced between arms. The OS hazard ratio (HR) was 0.807 (95% CI 0.678, 0.962; p=0.0169). Median OS was 9.63m for RAM+PTX and 7.36m for PTX. The HR for PFS was 0.635 (95% CI 0.536, 0.752; p <0.0001). Median PFS was 4.40m and 2.86m. Median TTP was 5.5m RAM+PTX; 3.0m PTX (p <0.0001). ORR was 28% RAM+PTX;16% PTX (p=0.0001). Grade ≥ 3 adverse events (AEs) occurring in >5% of patients on RAM+PTX were: neutropenia (40.7% RAM+PTX;18.8% PTX), leukopenia (17.4% vs 6.7% ), hypertension (14.1% vs 2.4%), anemia (9.2% vs 10.3%), fatigue (7.0% vs 4.0%), abdominal pain (5.5% vs 3.3%), and asthenia (5.5% vs 3.3%). Febrile neutropenia was reported in 3.1% RAM+PTX; 2.4% PTX. Conclusions: The primary endpoint of improved OS was met. A statistically significant and clinically meaningful OS benefit of > 2 months was observed for RAM+PTX vs. PTX in gastric and GEJ cancer after progression on 1st-line therapy, as were significant benefits in PFS and ORR. Neutropenia was more frequently reported in the RAM+PTX arm but incidence of febrile neutropenia was comparable between arms. Clinical trial information: NCT01170663.