The high tumor uptake and tumor:blood ratios observed in our xenograft studies with pegylated diabodies compares favourably with the results of other engineered antibody formats, including naked ~55kDa diabodies 7, ~85 kDa minibodies 37 and various scFv fusions and extensions to increase the systemic half-life such as scFv-Fc and scFv-albumin 15,38-39. This evidence concerns the gene ALB and neoplasm.