In vivo RAF signal transduction as a potential biomarker for sorafenib efficacy in patients with neuroendocrine tumours

Abstract

Background: Targeted therapies elicit anticancer activity by exerting pharmacodynamic effects on specific molecular targets. Currently, there is limited use of pharmacodynamic assessment to guide drug administration in the routine oncology setting.Methods:We developed a phosphoshift (pShift) flow cytometry-based test that measures RAF signal transduction capacity in peripheral blood cells, and evaluated it in a phase II clinical trial of oral sorafenib plus low-dose cyclophosphamide in patients with advanced neuroendocrine tumours (NETs), in order to predict clinical course and/or guide individual dose-titration.Results:Twenty-two patients were enrolled. Median progression-free survival (PFS) was 3 months (95% CI 2-10.7), and one patient had a partial response. PFS was longer among five patients who demonstrated an increase in pShift after 7 days of sorafenib compared with those who did not (14.9 months vs 2.8 months; P=0.047). However, pShift did not add value to toxicity-based dose-titration.Conclusion:The pharmacodynamic assessment of RAF transduction may identify selected patients with advanced NETs most likely to benefit from the combination of sorafenib plus cyclophosphamide. Further investigation of this test as a potential biomarker is warranted. © 2013 Cancer Research UK. All rights reserved.