Comparison of Interlesionally and Systemically Administered Radiolabelled Monoclonal Antibodies in Implanted Tumours

Abstract

In this experimental tumour system, intralesional administration (ILA) of ¹²⁵I labelled MAb increased uptake by a factor of three over systemic administration. Although there was an element of non-specific entrapment following ILA there was a 2.5 times greater uptake using a specific MAb (ALN/11/53) compared to a nonspecific control MAb (ICR-2). The areas of activity were demonstrated by autoradiography. After 24 hours, at the tumour muscle junction, activity tended to conform to the shape of the tumour. This suggests a potential advantage over conventional brachytherapy, however, a number of significant adverse features were encountered. In particular, there was significant leakage of radioactivity in the first 24 hours by backtracking along the needle and the volume of activity was small (< l/3rd of the tumour). Substantially more work is required to investigate methods to increase the distribution of activity throughout the whole tumour, reduce backtracking and measure its extent in larger tumours.