Phase II trial of everolimus in patients with refractory metastatic adenocarcinoma of the esophagus, gastroesophageal junction and stomach: possible role for predictive biomarkers.

PURPOSE

Our study was designed to evaluate the efficacy and safety of everolimus in patients with pre-treated metastatic gastric and esophagus cancers in a US-based population focusing on biomarker correlation.

METHODS

Patients with advanced upper GI adenocarcinomas who progressed after 1-2 prior regimens received everolimus 10 mg PO daily. The primary endpoint was disease control rate (DCR). Secondary endpoints included progression-free survival (PFS), toxicity, overall survival (OS) and biomarker correlatives of the mTOR pathway. Target accrual was 50 patients based on one-sided type I error of 10 % and power of 90 %.

RESULTS

Forty-five patients were evaluable, 21 gastric, 11 esophagus and 13 from the GEJ. The median age was 64 (range 38-73); all patients had an ECOG of 0 or 1; and 18 patients (40 %) had only 1 prior regimen. The most common grade 3-4 adverse events included fatigue (24 %) and thrombocytopenia (22 %). We observed 1 partial response with 39 % of evaluable patients having stable disease. Median OS was 3.4 months (95 % CI 2.7-5.6 months), and PFS was 1.8 months (95 % CI 1.7-2.2 months). There was a strong correlation between ≥2 + IHC staining for p-S6 in tumor samples with better PFS (p < 0.0001) and DCR (p = 0.0001).

CONCLUSIONS

Our clinical outcomes were inferior to the Asian studies, which may be explained by disease heterogeneity. However, there was a similar strong correlation between clinical benefit and tumor high pS6. Testing this biomarker in patient samples from the randomized phase III Granite trial may lead to a positive predictive marker.