revision preference src: PEO allows nanocarriers to travel through the leaky vasculature of a tumor, where they are unable to escape. The leaky vasculature of a tumor is the network of blood vessels that form in a tumor, which contain many small pores. <SEP> tgt: PEO allows nanocarriers to travel through the leaky vasculature of a tumor, where they are unable to escape. The leaky vasculature of a tumor is the vasculature of blood vessels that form in a tumor, which contain many small pores.