The future of prognostic factors in outcome prediction for patients with cancer.

The anatomic description of the extent of tumor spread (tumor staging) assists clinical management, facilitates communication among physicians, is an essential part of randomized controlled trials, and may help in the counseling patients and their families. However, in recent years, additional "prognostic factors" have been defined, many of which assess or reflect the biologic behavior of malignant neoplasms. Other measures of tumor biochemistry address the natural history of neoplastic development and often are included in a discussion of new prognostic factors. This review article summarizes current knowledge and thinking related to tumor prognostic factors in four areas by providing: (1) a definition and principles of anatomic spread of tumor (staging) and some suggestions for improvement, (2) a description of some examples of additional factors of prognostic significance, (3) some statistical methods to evaluate prognostic factors, and (4) an examination of the possible future of summary statements of outcome (i.e., prognostic indexes).