Horn et al. compared 18F-FLT and 18F-FDG for early measurement of response to sunitinib treatment in 20 patients with metastatic RCC and demonstrated that while 18F-FLT-PET could be used to identify response as early as one week after the start of treatment, 18F-FDG PET was more effective at a later time point of 3–4 weeks, suggesting that inhibition of VEGF signaling with sunitinib exerts an early effect on tumor proliferation, which is then followed by a reduction in tumor metabolism [66]. Here, VEGFA is linked to renal cell carcinoma.