Cancer Screening: A Review with Particular Attention to Areas for Future International Research Efforts.

For almost all of the sites of most common cancers, particularly the lung, colo-rectum and cervix, relatively inexpensive and reliable tests have been available for some time. Advances in imaging techniques now allow identification of early tumours in many other organs, including those that are normally associated with a very poor prognosis. In addition, increasing knowledge of the risk factors for cancer development in different organs imply more effective screening for early malignancies in high risk populations and the associated increase in the predictive value should mean that early intervention will result in a marked decrease in the mortality and morbidity due to a wide range of major cancers. However, there are many difficulties which remain to be overcome, especially in the psychosocial area. Problems with overdiagnosis and distinction of lesions most likely to actually give rise to cancers also require especial attention for the full promise of screening to be realised. In addition, choice of the most appropriate approach will require an in depth understanding of cultural factors impacting on screening behaviour and it is of paramount importance that both physicians and the public at large be fully aware of pitfalls and potential benefits. Thus research needs to be concentrated on effective education approaches as well as how to increase practical sensitivity and specificity of individual tests and determine the best follow-up for individuals testing positive.