Phase II randomized study of maintenance therapy with regorafenib (REGO) versus placebo after first-line platinum and fluoropyrimidines-based chemotherapy in HER2 negative locally advanced/metastatic gastric (GC) or gastroesophageal junction (GEJ) cancer: Results of a-MANTRA study (GOIRC-05-2016).

Abstract

4056 Background: REGO is an oral multi-targeted TKI that showed promising activity in advanced HER2-neg gastric cancer pts. The a-MANTRA study aimed to evaluate the efficacy and safety of REGO as maintenance after first-line (1L) therapy in advanced GC/GEJ tumors. Methods: This is a randomized, double-blind, placebo-controlled, multicenter Phase-II study in which HER2 neg advanced GC/GEJ pts with disease control after 1L platinum and fluoropyrimidines-based therapy, were randomized (1:1 ratio) to receive maintenance placebo (ARM A) or REGO (ARM B) starting at 80 mg with an escalation up to 160 mg (once daily on d1-21 q28 days), until intolerance or PD. The primary endpoint was Progression Free Survival 1 (PFS1). Two-sided 80% CIs were calculated to detect HR of 0.57, using a one-sided α=0.10 to have 90% power, translating to 3 months of improvement in mPFS. 118 subjects were required to observe 88 events. The interim analysis (IA) was planned after 44 events. Results: 67 pts were randomized in 18 Italian Cancer Centers; 64 pts (33 in ARM A and 31 in ARM B) received treatment. Most of the pts were male (64.1%), Caucasian (96.8%), ECOG PS 0 (81.2%), and median age 66 (40-80) yrs; the main primary tumor side was proximal (64.1%) with intestinal subtype (54.7%). Peritoneum metastases were present in 42.2%. IA showed a 98% probability of achieving a positive and statistically significant result for mPFS1. The study was stopped early due to the introduction of ICIs as 1L in PD-L1-positive pts. The objective responses to 1L chemotherapy were RP (50.0%), SD (42.2%), and CR (7.8%). At a median follow-up of 31 months (IQR 19.1-33-8), 28 (84.8%) and 26 (83.8%) events for each arm were reported. The main reason for discontinuation was PD (66.7% and 35.5%). The mPFS was 3.91 (80% CI, 2.27-5.98) and 5.19 months (80% CI, 4.0-7.26) with HR= 0.736 (80%CI, 0.51-1.04; p=0.1318). The mOS was 11.25 and 16.97 months (80%CI, HR=0.596 [0.318-1.103], p=0.1003). The most common G3-4 toxicities in ARM A and B were fatigue (3.0 vs 6.4%), thrombocytopenia (3.0 vs 3.2%), hand-foot syndrome (0 vs 12.9%), diarrhea and skin rash (0 vs 3,2%, respectively). Conclusions: Despite the promising trend, considering the sample was not sized for the statistical study hypothesis, REGO maintenance therapy after 1L chemotherapy did not reach statistically significant results in mPFS1. No significant safety concerns were raised. New study designs following the REGO with ICIs are currently underway. Clinical trial information: NCT03627728 .