Figure 6.

Flow chart summarizing survival data shows the multistep nature of metastatic inefficiency: percentages of injected cells remaining as solitary cells, or forming micrometastases or macroscopic tumors, at different times after injection (p.i.). (At 90 minutes, >85% of injected cells were intravascular, whereas by 3 days, >80% had completed extravasation.) Note the slow loss of solitary cells with time. Dotted arrows indicate possible origins of micrometastases and macroscopic tumors. Two distinct steps after extravasation were principal determinants of metastatic inefficiency: failure of solitary cells to initiate growth and failure of micrometastases to continue growth into macroscopic tumors.