In one aspect, the invention includes a composition for treating a tumor in a subject, comprising liposomes composed of a vesicle forming lipid and between about 1 20 mole percent of {HEAD ~ a vesicle forming lipid} derivatized with {TAIL ~ a hydrophilic polymer} 
derivatized with
In one aspect , the invention includes a composition for treating a tumor in a subject , comprising liposomes composed of a vesicle forming lipid and between about 1 20 mole percent of { HEAD ~ a vesicle forming lipid } derivatized with { TAIL ~ a hydrophilic polymer }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL