Cancer detection can be defined as the search for and identification of cancer or its precursors in the asymptomatic, presumably healthy individual by means of a standardized routine examination.

Detection Vs. Diagnosis

Cancer detection is to be contrasted with cancer diagnosis which usually refers to the identification of the disease in an individual as a result of physical, laboratory, or other examinations prompted by specific symptoms or complaints. If not found first by a cancer detection examination, presumably all such malignant lesions will declare themselves eventually and yield to efforts at cancer diagnosis.

Such a distinction between detection and diagnosis is not a mere academic exercise in precise semantics. The belief that there is biologic justification for such a distinction in clinical cancer is a tacit reflection of principles which provide the rationale, direction, and scope of present-day efforts at cancer control. This will become evident in succeeding paragraphs.

Rationale Of Cancer Detection

Efforts to promote the more widespread adoption of cancer detection examinations in the physician's office make certain assumptions:

1. In many instances cancer is preceded for a period of months or years by a microscopically benign lesion which ultimately becomes or gives rise to microscopically and clinically malignant disease. Removal of such lesions prevents the subsequent development of cancer. This is true cancer prevention.

2. Most cancer at its inception goes through a phase in which it is quite localized either at the cellular or organ level. If cancer is found at this stage, a high rate of cure is obtainable.

3. Over 75% of cancer occurs in areas which are readily accessible to periodic survey by reliable cancer detection procedures.

4. Although far from ideal, present-day methods of treatment are often very effective when applied early enough.

5. In most sites and in most cases there is a clearly demonstrable relationship between early diagnosis and good prognosis.

No claim is made that this search for and treatment of the early case is the ideal approach to the problem or that it is always successful. Perhaps before long it will be supplanted by a new method oriented to a quite different concept of the disease, more reliable, less expensive and time consuming, and, most important of all, more effective.

However, it can be safely said that in the light of our current understanding of the disease and considering the clinical laboratory and treatment methods now available, programs of cancer control which emphasize the detection and early diagnosis (and, as will be pointed out in regard to a few sites, prevention) of cancer and its precursors afford the best protection possible for the individual and the community at present.

The concept of premalignant lesions and localized cancer, and especially the relationship of these to prognosis and curability, has been dealt with in Chapter I (The Cancer Problem).

In this chapter it is assumed that detection and early diagnosis are definitely related to curability, and steps are outlined whereby this fact can be exploited by means of a routine history, physical examination, and laboratory survey in asymptomatic individuals.