Prediction of prognosis in patients treated with everolimus for extrapancreatic neuroendocrine tumors by a single nucleotide polymorphism in PHLPP2.

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163 Background: Rapamycin analogs (rapalogs) have improved outcomes in patients with neuroendocrine tumors (NETs). Few factors affecting response to rapalogs have been characterized. PHLPP2 is a phosphatase that inhibits PI3K-Akt-mTOR signaling. We hypothesized that an inactivating single nucleotide polymorphism (SNP) in PHLPP2 may affect outcomes in NETs treated with the rapalog everolimus. Methods: Blood was collected from 32 patients enrolled in a Phase 2 single arm trial of single agent everolimus in patients with NETs. DNA was extracted and RT-PCR products were sequenced to detect the L1016S SNP in PHLPP2. Outcomes analyses determined the role of the SNP in predicting progression-free survival (PFS), overall survival (OS), and response rates (RR) in patients with NETs treated with everolimus. Response rate (RR) assessed by RECIST criteria was evaluated as a binomial endpoint. A subset analysis was conducted to evaluate the NET site-specific role of the SNP. Results: Overall median PFS was 15.2 months (95% Confidence Interval (CI)=11.5 -18.7). The PHLPP2 SNP did not predict for a significant difference in PFS (Median PFS; wild type vs. SNP 16.8 (95% CI=14-20) vs. 11.3 (95% CI=4-19) mos., respectively, Hazard Ratio (HR)=1.2 (95% CI=0.5-3.1)), p=0.154). In a subset analysis, patients with extra-pancreatic NETs treated with everolimus with wild type PHLPP2 demonstrated increased PFS compared to patients with the SNP (Median PFS = 16.8 (95% CI=7-26) vs. 7.7 (95% CI=6-9) mos., HR=10.8 (95% CI=2-67), p=0.002). OS and RR were unaffected by the presence of the SNP in all analyses. Conclusions: In this preliminary study, the L1016S SNP in PHLPP2 may be prognostic for poorer PFS in patients with extrapancreatic NETs treated with everolimus. This study is hypothesis generating and requires validation in larger retrospective and randomized, placebo controlled studies in patients with NETs treated with everolimus.