Conclusions

Summary

Overview

The geographical and temporal variations in cancer incidence and migrant studies, complemented by analytical epidemiological investigations on cultural and occupational cancers, led to the view that most human cancers have a significant environmental component (pp. xxi–xxiv). Such studies indicated the considerable possibilities of cancer prevention, either by removal or reduction of exogenous carcinogens, through modification of ‘lifestyle’ factors, especially tobacco and diet, or by active intervention using vaccines, drugs or other agents during the pre-neoplastic phase. Today, it is recognized that interaction between environmental and genetic factors may also be of great importance for specific subsets of the population (Chapter 18). None the less, while there is a general consensus on the probable causes of many human cancers, specific preventive measures cannot yet be recommended with any certainty for about 50% of cancers in males and 70% in females in industrial states (Higginson, 1988; Muir, 1990; Schmahl et al., 1989).

Contribution of known or suspected causes

Estimates based on the available literature have been made in a number of countries of the contribution to the total cancer burden of a variety of defined or suspected causes. Such estimates include those of Wynder and Gori (1977), Higginson and Muir (1979) for morbidity and Doll and Peto (1981) for mortality (Tables 1 and 2).