Introduction

Carcinogenesis is a multi-factorial, multistep process involving cancer induction by a range of mechanisms which may vary both by agent and neoplasm. While it is considered that some form of DNA damage is essential to the process and that a cascade of other events is involved, the extent and nature of the damage and the specific role of many phenomena seen in carcinogenesis remain to be elucidated. In this context, there is a growing body of laboratory methods that can be utilized to amplify the role of epidemiology in the study of carcinogenic processes. Such approaches are relevant to the following areas :

1. (a) The diagnosis and determination of the pathogenesis of neoplasms, including preneoplastic end-points.

2. (b) Methods to measure present and past exposures to suspected carcinogenic agents, both quantitatively and qualitatively, that is, biomarkers of exposure.

3. (c) Methods to measure exposure to certain nutrients potentially associated with human cancer, i.e. biomarkers that reflect dietary influences with varying degrees of specificity.

4. (d) Provision of objective end-points for determining individual and tissue susceptibility.

5. (e) Provision of data on the carcinogenic mechanisms involved, including metabolic pathways.

This chapter discusses certain general concepts and techniques. Other aspects are discussed under individual cancer sites, as well as in Chapters 17 and 18.

Application of morphological and cytological techniques

Diagnosis of cancer

The validity of descriptive and analytical epidemiological data is greatly influenced by the accuracy of the diagnosis. Accurate diagnosis of tumors reduces misclassification, permits sub-classification and thus improves the possibility of demonstrating causal associations.