Cancer detection tests can be divided rather simply into two groups: (1) those which purport to indicate the presence of the disease anywhere in the individuals body and (2) those which point to the presence of cancer in a specific single organ or site.

The purpose of a cancer detection test is to single out from a large group surveyed those relatively few individuals in whom a diagnosis or suspicion of cancer is suggested by this screening process. These patients can then be subjected to more intensive evaluation by conventional diagnostic measures.

Criteria For Cancer Detection Tests

The ideal cancer detection test, whether general or site-specific, should possess the following characteristics:

1. Simplicity. The procedure should be uncomplicated, easily and quickly carried out, with a minimum of discomfort to the patient. It should be adaptable for screening large numbers of patients.

2. Low cost. The procedure should be inexpensive in terms of equipment required and professional and technical time consumed.

3. Reliability. The percentage of false positives must be kept to a minimum.

4. Sensitivity. The percentage of false negatives must also be low. Furthermore, the procedure must be capable of detecting disease in its early, localized stages.

5. Productivity. Assuming a test is sensitive and reliable, the yield of cancer is a reflection of the incidence of the disease rather than the procedure itself.

It is immediately apparent that these criteria are not absolute but are relative. Not only that, they are interdependent. For example, proctosigmoidoscopy is not exactly a "simple" procedure. However, what it lacks in simplicity it more than makes up in reliability and productivity. On the other hand, whatever virtues screening or detection methods for bone tumors, pheochromocytomas, etc., might have in terms of simplicity, reliability, sensitivity, etc., are canceled out by the very low yield to be expected. The final assessment of the value of a cancer detection method lies in a critical evaluation of the number of these criteria it satisfies and to what degree.