Cancer metastasis

Understanding of the process by which tumor cells develop heterogeneity, invade local tissues, and spread to distant tissues is a major goal of cancer research, as it will determine whether clinicians will be able to design more effective therapies for different cancers. Although much has been learned, much remains to be learned. The following summarizes our current knowledge about metastasis: 1. Cancer is the result of transformation of single cells. 2. Transformed cells are less stable and have an increased rate of spontaneous mutation than non-metastatic cells of similar origin. 3. Cells within a tumor are heterogeneous in biological characteristics. 4. The metastatic process is selective for highly malignant cells from within the heterogeneous tumor. 5. The metastatic process is a complex sequence of events with an outcome dependent on both tumor cell and host properties. 6. By the time of diagnosis, many primary solid tumors are biologically heterogeneous and have disseminated to regional or distant sites. 7. By the time of initial diagnosis, metastases in some state of development are thought to exist in approximately 50% of patients. 8. Cancer metastasis is the major cause of treatment failure and mortality in individuals with malignant tumors. The complexity and diversity of human cancer, in conjunction with the complexity and diversity of human beings diagnosed with cancer presents a major challenge to oncology clinicians and researchers.