New Agents for the Treatment of Acute Lymphoblastic Leukemia

The majority of cancers present at a relatively advanced stage in which invasion within the primary organ is well established and metastases to lymph and distant organs are either clinically apparent or present at the microscopic level. However, it is increasingly recognized that the natural history of cancer formation is a long and complex path taking many years to develop to a clinically apparent stage in most cases. Furthermore, for most solid tumours there is a pre-invasive or intraepithelial stage of disease. This affords the opportunity for early detection and prevention of invasive disease and hence a cure. However, with this advancing knowledge comes a whole plethora of questions which will be explored in this monograph.

Firstly, we need to understand the global burden of pre-invasive disease and what the public health implications might be for wide-scale screening programmes. In the western world we already have experience of screening for cervical, breast, prostate and more recently colon cancer. As well as their potential benefits these programmes have financial and psychosocial implications which need to be carefully weighed. This is especially true since many pre-invasive lesions will not progress to cancer in a individual's lifetime. In addition, there are questions concerning whether screening reduces the cancer burden or in fact distorts the survival figures through lead-time bias.

Secondly, at the level of epidemiology and molecular pathogenesis there are important questions regarding the aetiology of pre-invasive lesions; an understanding of which might lead to possible chemopreventive strategies. For example, it would be helpful to know the extent to which the likelihood of developing a pre-invasive lesion is influenced by lifestyle or genetic factors and how these factors influence the risk of progression to invasive disease. At the molecular level we need to understand the pathways and molecular mechanisms, both genetic and