ALB and neoplasm: After 30 min, the LNCaP tumors cumulated 2.5 ± 0.5% of the circulating radioactivity which increased to 33.5 ± 16% after 24 h (Fig. 5B), indicating an efficient tumor-specific release of the modified PACE4 inhibitor (SL[4-Apaa]K(64Cu/NOTA)LLLLRVKR-NH2) as a part of the albumin-bound probe and a great stability of the injected conjugate in circulation.