ON THE GROWTH-RATES OF HUMAN-MALIGNANT TUMORS - IMPLICATIONS FOR MEDICAL DECISION-MAKING

Testicular carcinomas, pediatric tumors, and some mesenchymal tumors a re examples of rapidly proliferating cell populations, for which the t umor volume doubling time (TVDT) can be counted in days. Cancers from the breast: prostate, and colon are frequently slow-growing, displayin g a TVDT of months or years. irrespective of their growth rates, most human tumors have been found: to start from one single cell, to have a long subclinical period, to grow at constant rates for long periods o f time, to start to metastasize often even before the primary is detec ted, and to have metastases that often grow at approximately the same rate as tile primary tumor. The recognition of basic facts in tumor ce ll kinetics is essential in the evaluation of important present-day st rategies in oncology, Among the facts emphasized in this review are: ( 1) Screening programs. Most tumors are several years old when detectab le by present-day diagnostic methods. This makes the term ''early dete ction'' questionable. (2) Legal trials. The importance of so-called do ctor's delay is often discussed, bur the prognostic value of ''early'' detection is overestimated (3) Analyses of clinical trials. Such anal ysis may be differentiated depending on the growth rates of the type o f tumor studied. Furthermore, uncritical analysis of survival data may be misleading if the TVDT is not taken into consideration. (4) Analys es of epidemiological data. If causes of malignant tumors in humans ar e searched for, the time of exposure must be extended far back in the subject's history. (5) Risk estimations by insurance companies. For th e majority of human cancers, the 5-year survival rate is not a valid m easurement for cure, Thus, basic knowledge of tumor kinetics may have important implications for political health programs, legal trials, me dical science. and insurance policies. (C) 1997 Wiley-Liss, Inc.