Deprimo SE, Huang X, Blackstein ME, Garrett CR, Harmon CS, Schöffski P, Shah MH, Verweij J, Baum CM, Demetri GD. Circulating levels of soluble KIT serve as a biomarker for clinical outcome in gastrointestinal stromal tumor patients receiving sunitinib following imatinib failure.
Clin Cancer Res 2009;
15:5869-77. [PMID:
19737953 DOI:
10.1158/1078-0432.ccr-08-2480]
[Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
PURPOSE
To evaluate changes in circulating levels of soluble KIT (sKIT) extracellular domain as a potential biomarker for clinical outcome in gastrointestinal stromal tumor patients treated with the multitargeted tyrosine kinase inhibitor sunitinib following imatinib failure in a previously reported phase III study.
EXPERIMENTAL DESIGN
Patients received sunitinib 50 mg/d (n = 243) or placebo (n = 118) daily in 6-week cycles (4 weeks on, 2 weeks off treatment). Plasma sKIT levels were sampled every 2 weeks in cycle 1 and on days 1 and 28 of subsequent cycles; analyzed by ELISA; and evaluated using Prentice criteria, Cox proportional hazards models, and proportion of treatment effect (PTE) analysis.
RESULTS
From 4 weeks on treatment and onward, significant differences were shown between treatment groups (P < 0.0001) in sKIT level changes from baseline (median levels decreased with sunitinib and increased with placebo). Decreases in sKIT levels were a significant predictor of longer time to tumor progression (TTP). Patients with reduced levels at the end of cycle 2 had a median TTP of 34.3 weeks versus 16.0 weeks for patients with increased levels [hazard ratio, 0.71; 95% confidence interval (95% CI), 0.61-0.83; P < 0.0001], and changes in sKIT levels replaced treatment as a stronger predictor of TTP (PTE, 0.80; 95% CI, 0.34-3.70), showing even greater surrogacy on cycle 3 day 1 (PTE, 0.98; 95% CI, 0.39-3.40).
CONCLUSIONS
The results suggest that circulating plasma sKIT levels seem to function as a surrogate marker for TTP in gastrointestinal stromal tumor patients. Additional studies are warranted to confirm and expand these findings.
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