Olecranon bursitis in patients treated with sunitinib for renal cell carcinoma.

Sunitinib is a recently approved tyrosine-kinase inhibitor that targets the vascular endothelial growth factor receptors (VEGFR). We report two cases of patients with metastatic renal cell cancer who developed olecranon bursitis while receiving sunitinib. In both cases other causes of bursitis were excluded and the symptoms resolved after treatment with sunitinib was discontinued. Recurrence of symptoms during subsequent treatment cycles was also observed. This adverse event has not been previously reported for sunitinib and we believe it is directly attributable to the drug. This is an unexpected adverse event, given the mechanism of action of the drug. The pathophysiology of this event remains unexplained, although we describe some hypotheses.