No validated predictive biomarkers for antiangiogenic treatment of metastatic renal cell carcinoma (mRCC) exist. Tumor vascular endothelial growth factor A (VEGF-A) level may be useful. We determined tumor uptake of 89 Zr-bevacizumab, a VEGF-A-binding PET tracer, in mRCC patients before and during antiangiogenic treatment in a pilot study. Methods: Patients underwent 89 Zrbevacizumab PET scans at baseline and 2 and 6 wk after initiating either bevacizumab (10 mg/kg every 2 wk) with interferon-α (3-9 million IU 3 times/wk) (n 5 11) or sunitinib (50 mg daily, 4 of every 6 wk) (n 5 11). Standardized uptake values were compared with plasma VEGF-A and time to disease progression. Results: 89 Zrbevacizumab PET scans visualized 125 evaluable tumor lesions in 22 patients, with a median SUV max (maximum standardized uptake value) of 6.9 (range, 2.3-46.9). Bevacizumab/interferon-α induced a mean change in tumor SUV max of −47.0% (range, −84.7 to 120.0%; P , 0.0001) at 2 wk and an additional −9.7% (range, −44.8 to 138.9%; P 5 0.015) at 6 wk. In the sunitinib group, the mean change in tumor SUV max was −14.3% at 2 wk (range, −80.4 to 1269.9; P 5 0.006), but at 6 wk the mean change in tumor SUV max was 172.6% (range, −46.4 to 1236%; P , 0.0001) above baseline. SUV max was not related to plasma VEGF-A at all scan moments. A baseline mean tumor SUV max greater than 10.0 in the 3 most intense lesions corresponded with longer time to disease progression (89.7 vs. 23.0 wk; hazard ratio, 0.22; 95% confidence interval, 0.05-1.00). Conclusion: Tumor uptake of 89 Zr-bevacizumab is high in mRCC, with remarkable interpatient and intrapatient heterogeneity. Bevacizumab/interferon-α strongly decreases tumor uptake whereas sunitinib results in a modest reduction with an overshoot after 2 drugfree weeks. High baseline tumor SUV max was associated with longer time to progression.

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Prostate cancer is a critical public health problem in USA and Europe. New non-invasive imaging methods are urgently needed, due to the low accuracy and specificity of current screen methods and the desire of localizing primary prostate cancer and bone metastasis. Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) are the non-invasive and sensitive imaging methods which have been widely used for diagnosing diseases in the clinic. Lack of suitable radiotracers is the major issue for nuclear imaging of prostate cancer, although radiolabeled bombesin (BN) peptides targeting the Gastrin-Releasing Peptide Receptor (GRPR) on tumor cells are widely investigated. In this review we discuss the recent trends in the development of GRPR-targeted radiopharmaceuticals based on BN analogs with regard to their potential for imaging and therapy of GRPR-expressing malignancies. Following a brief introduction of GRPR and bombesin peptides, we summarize the properties of prostate cancer specific radiolabeled bombesins. New bombesin tracers published in the last five years are reviewed and compared according to their novelties in biomolecules, radionuclides, labeling methods, bifunctional chelators and linkers. Hot topics such as multimerization, application of agonists and antagonists are highlighted in the review. Lastly, a few clinical trials of cancer nuclear imaging with radiolabeled bombesin have been discussed.