Figure 5. Inefficiency of the Invasion-Metastasis Cascade: Metastatic Colonization is Often Rate-Limiting.
Certain steps of the invasion-metastasis cascade are successfully completed with only extraordinary inefficiency. Work in experimental models has revealed that the process of metastatic colonization typically represents the rate-limiting step of the invasion-metastasis cascade, with a rate of attrition that often exceeds 99% of those cells that initially survive in a foreign microenvironment to form micrometastases. Red x-marks denote the approximate cumulative fraction of intravenously implanted tumor cells that have died after passage through the indicated steps of the invasion-metastasis cascade.