There is increasing use of tyrosine kinase inhibitors as targeted therapy for several malignancies. Sunitinib is the first-line treatment for renal cancer and we report a case of a man receiving this medication who also had diabetes. When started on sunitinib he experienced improvement in his diabetes control with reduction in his insulin requirements, which later worsened when sunitinib was reduced or stopped. Several retrospective studies have been performed demonstrating this effect with sunitinib, but to date no prospective studies have been reported. Most tyrosine kinase inhibitors reduce blood glucose levels in diabetics, but some agents, such as nilotinib, may increase them. There is no consensus on the mechanism of action of sunitinib in reducing glucose levels. Several theories have been postulated, such as increased insulin secretion, increased insulin sensitivity, reduced loss of islet cells, the gastrointestinal side effects of sunitinib, or an interaction with other antihyperglycaemic agents.
2014 BMJ Publishing Group Ltd.