Single-fraction irradiation has no effect on uptake of radiolabeled pegylated liposomes in a tumor xenograft model

Purpose: These studies were performed with the intention of examining the e ffect of single-fraction doses of radiotherapy (RT) on the tumor deposition of radiolabeled pegylated liposomes in an animal xenograft tumor model. Methods and Materials: Human KB head-and-neck xenograft tumors were establi shed in female nude mice. The effect of single fraction tumor RT doses (5, 10, 15, and 20 Gy) on the tumor uptake of intravenously administered In-111 -DTPA-labeled pegylated liposomes (IDLPL) was examined using two protocols: (I) to test the effect of RT delivered 30 min before liposome injection on the time course of tumor uptake over a 96-h period; (2) to test the effect of RT at times ranging from 72-h to l-h before liposome injection on the l evels of liposome uptake at 24 h, Tumor and normal tissue/organ (blood, liv er, spleen, lung, and kidney) liposome uptake was determined by dissection and quantitation in a gamma counter. Results: There was no demonstrable effect of RT on tumor uptake of IDLPL (p > 0.1 for all comparisons). Reassuringly, neither was there an effect of R T on the pharmacokinetics and biodistribution of radiolabeled liposomes to normal tissues. Conclusions: Single fraction doses of RT appear to have no effect on tumor or normal tissue biodistribution and pharmacokinetics of radiolabeled pegyl ated liposomes in this animal model, (C) 2001 Elsevier Science Inc.