Influence of tumour size on uptake of In-111-DTPA-labelled pegylated liposomes in a human tumour xenograft model

The relationship between tumour size and uptake of In-111-DTPA-labelled peg ylated liposomes has been examined in a human head and neck cancer xenograf t model in nude mice. The mean tumour uptake of In-111-labelled pegylated l iposomes at 24 hours was 72 +/- 6.6% ID/g. Liposome uptake for tumours < 0. 1 g, 0.1-1.0 g and > 1.0 g was 15.1 +/- 10.8, 5.9 +/- 2.2 and 3.0 +/- 1.3% ID/g, respectively. An inverse correlation between tumour weight and liposo me uptake was observed by both Spearman's rank correlation test (r(s) = -0. 573, P < 0.001) and Pearson's correlation coefficient (r(s) = -0.555, P < 0 .001). For 18 tumours with macroscopic central necrosis, the ratio of uptak e in the tumour rim relative to the necrotic tumour core was 11.2 +/- 6.4. Measurement of tumour vascular volume for tumours of various sizes revealed an inverse correlation between tumour weight and tumour vascular volume (S pearman's rank correlation test, r(s) = -0.598, P < 0.001), consistent with poor or heterogeneous vascularization of larger tumours, These data have i mportant implications for the clinical application of pegylated liposome ta rgeted strategies for solid cancers which are discussed in detail. (C) 2000 Cancer Research Campaign.