Natural Growth Rate of Primary Breast Cancer and its Metastases

Abstract

Patients suffering from breast diseases generally die when metastatic spread into the bloodstream occurs. When distant metastases become clinically manifest the survival rates are about the same with various types of palliative therapy. Wide individual differences can be observed, however, in the interval between diagnosis of the primary tumor and development of local recurrences and detection of distant metastases. This interval varies from zero (distant metastases present at time of primary diagnosis) to more than 30 years, Brinkley and Haybittle [6,7] showed that after a follow-up of 25 years, 81.5% of women had died after breast cancer, leaving only 18.5% still alive. As metastatic spread does not necessarily begin preoperatively, wide differences can be observed in the time the metastases take to reach a clinically detectable size. This is primarily due to the two following growth behaviors of the metastases:

• 1. The net metastatic growth varies; it may be extremely slow because of cell loss. As far as the speed of growth of the whole tumor is concerned, no significant changes can be observed; this behavior can be represented by a relatively uniform exponential function.

• 2. The growth behavior of metastatic cells is very heterogeneous. After a period of dormancy the cells may suddenly grow very rapidly because of a change in the host-tumor relation. This heterogeneity seems to be most important in the early stage of metastatic spread (100–1000 cells). At the time of detection (several hundred thousand cells), the differing growth behavior of individual cells is thought to play only a minor role.