Distant metastases (MET) are for most solid cancers decisive life-threatening events. Data about MET-free survival and survival after MET show a strong dependency on the kind of cancer and the prognostic features. Nonetheless, within biological subgroups, the MET process is very homogenous. Therefore, the growth rate can be estimated from initiation of MET to MET diagnosis and to time of death. Based on the known volume doubling time of breast cancer, the time of the first possible dissemination can also be estimated. Important consequences of these MET-initiation estimates are the hypotheses that almost all MET are initiated before removal of the primary tumor and that MET do not metastasize in a clinically relevant magnitude. Although breast cancer data were primarily used to form these hypotheses, the discussed MET process can be generalized to all solid cancers. The impact of these hypotheses on diagnostic, curative and palliative treatment, aftercare, and especially on clinical research would be important.