Understanding barriers to drug delivery: high resolution in vivo imaging is key.

In this issue of Clinical Cancer Research , Lankelma et al. [(1)][1] report on doxorubicin gradients in biopsies of breast tumors from patients. The gradients are pronounced 2 h after i.v. injection and become negligible 24 h later. Gradients of anthracyclins in tumor spheroids [(2][2] [, 3)][3] ,

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