Introduction

Introduction

In western countries malignant tumours originating from colorectal carcinoma are
frequently seen in the liver. Surgical resection is presently the treatment of choice in
patients with liver metastases. After this procedure the 5-year survival is around 35%
[1]. However, most tumours are inoperable by the time of diagnosis. Other treatment
options for these tumours include conventional chemotherapy and external
radiotherapy [2,3]. Unfortunately, neither of the latter regimens have shown an
obvious improvement in patient survival. The regional administration of therapeutic
agents [4] via the hepatic artery is one strategy that has been developed to improve
tumour response, since both primary and metastatic liver tumours are well
vascularized and receive the bulk of their blood supply from the hepatic artery [5].
These therapies must satisfy two requirements in order to be successful: (a) the
relevant agent must be effective in the in-vivo orthotopic microenvironment of
tumours, and (b) this agent must reach the target cells in-vivo in optimal quantities
[6]. All conventional and novel therapeutic agents for regional administration may be
divided into three categories: molecules, particles and cells. In this review we focus on
the injection of particles into the hepatic artery in order to obtain selective delivery of
radioisotopes to the tumour, thus maximizing the irradiation effect while sparing
toxicity to the surrounding healthy liver [2]. Among the more promising of these
radiotherapeuticals are beta-emitting microspheres. These microspheres can be based
on polymers, polymeric resins, albumin or inorganic materials e.g. glass.
Radioisotopes used for labeling are yttrium-90 (90Y), rhenium-186/rhenium-188
(186Re/188Re) and holmium-166 (166Ho).
This chapter reviews the current literature on radioactive microspheres used for the
treatment of liver malignancies and concludes with the aims and outline of the thesis.