An exploratory study of metformin (Met) with or without rapamycin (Rapa) as maintenance therapy after induction chemotherapy in patients (Pts) with metastatic pancreatic adenocarcinoma (PDA).

Abstract

700 Background: Few studies have examined maintenance therapy in unselected pts with metastatic PDA (mPDA). mTOR signaling is central to several oncogenic pathways in PDA and also has a role in T cell differentiation and activation, and we hypothesized a role for mTOR inhibition (mTORi) in the maintenance setting. Methods: This was a randomized open-label study conducted at 2 sites. Eligible pts had mPDA with stable disease for ≥6 months on chemotherapy and ECOG PS 0/1. Pts were randomized 1:1 to Met 850mg BID alone (Arm A) or with Rapa 4mg daily (Arm B), stratified by prior FOLFIRINOX. Baseline and on-treatment PET scans and peripheral blood mononuclear cells were obtained for exploratory analyses. Results: 23 pts were randomized. Median age was 64 (range 34-77) and 82% had ECOG PS 1. 12 of 23 received prior FOLFIRINOX; 8 received >1 prior line of therapy. 22 subjects (11 per arm) were treated per protocol. Treatment related adverse events of Grade ≥3 were seen in 0% vs 27% of pts in Arm A vs B and were all asymptomatic hematologic or electrolyte abnormalities that were not clinically significant. Median PFS/OS were 3.5 (95% CI: 2.9-9.2)/13.2 mos (95% CI: 7.8 to not reached) respectively, with 2 yr OS rate of 37% (95% CI: 21-66%); there were no differences between treatment arms. As expected in the maximally debulked setting, no responses were observed by RECIST; however, decreases in FDG avidity and/or CA199 were observed in several long-term survivors. Better survival was associated with low baseline neutrophil to lymphocyte ratio, baseline lack of assessable disease by PET, and with expansion of dendritic cells following treatment. Compared to Met alone, Met + Rapa was associated with decreased mTOR activity on some immune cell subsets and decreased metabolic fitness, but this was not correlated with outcome. Conclusions: Met +/- rapa maintenance for mPDA was well-tolerated and several pts achieved stable disease associated with exceptionally long survival. Further prospective studies are needed to clarify the role of mTORi in the maintenance setting and to enhance pt selection for such approaches. Clinical trial information: NCT02048384.