CXCR4 and neoplasm: The radiotracer 14 displayed excellent biodistribution in mice bearing OH-1 h-SCLC tumors with higher uptake in tumors (6.16 ± 1.16% ID/g) and significantly lower uptake in the liver (1.85 ± 0.24% ID/g) at 1 h p.i. The tumor-to-blood (5.8 ± 0.9) and tumor-to-muscle (16.6 ± 3.8) ratios for 14 were also considerably higher than those found for other peptidic CXCR4 radiotracers.