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Dynamic contrast-enhanced magnetic resonance imaging pharmacodynamic biomarker study of sorafenib in metastatic renal carcinoma.

PURPOSE
Sorafenib is an antiangiogenic agent with activity in renal cancer. We conducted a randomized trial to investigate dynamic contrast magnetic resonance imaging (DCE-MRI) as a pharmacodynamic biomarker.


PATIENTS AND METHODS
Patients were randomly assigned to placebo or 200 or 400 mg twice per day of sorafenib. DCE-MRI was performed at baseline and 4 weeks. DCE-MRI parameters, area under the contrast concentration versus time curve 90 seconds after contrast injection (IAUC(90)), and volume transfer constant of contrast agent (K(trans)) were calculated for a metastatic site selected in a blinded manner. Primary end point was change in K(trans).


RESULTS
Of the 56 assessable patients, 48 underwent two MRIs; 44 MRIs were assessable for study end points. Mean K(trans) log ratios were 0.131 (standard deviation [SD], 0.315), -0.148 (SD, 0.382), -0.271 (SD, 0.499) in placebo, 200- and 400-mg cohorts, respectively (P = .0077 for trend) corresponding to changes of +14%, -14%, and -24%. IAUC(90) log ratios were 0.041 (SD, 0.197), -0.040 (SD, 0.132), -0.356 (SD, 0.411), respectively (P = .0003 for trend), corresponding to changes of +4%, -4%, and -30%. Using a log-rank test, IAUC(90) and K(trans) changes were not associated with progression-free survival (PFS). Patients with high baseline K(trans) had a better PFS (P = .027).


CONCLUSION
IAUC(90) and K(trans) are pharmacodynamic biomarkers for sorafenib, but variability is high and magnitude of effect is less than previously reported. Changes in DCE-MRI parameters after 4 weeks of sorafenib are not predictive of PFS, suggesting that these biomarkers are not surrogate end points. The value of baseline K(trans) as a prognostic or predictive biomarker requires additional study.