The metastatic process: basic research and clinical implications.

Metastatic spread of cancer is responsible for most deaths due to cancer. An understanding of the process of metastasis at a level sufficient to permit the development of effective antimetastatic therapies thus has the potential to make an impact on mortality from cancer. Recent experimental studies using in vivo videomicroscopy, which have allowed direct observation and quantification of steps in metastasis as they occur in vivo, have led to new insights into the metastatic process and steps that result in metastatic inefficiency. It is important to learn if these findings are relevant to clinical cancer. If these experimental results reflect the situation that occurs during metastasis of human cancers, there are clinical implications that deserve evaluation. In this Commentary, these results are discussed in the context of human cancer, and the possible clinical implications of the experimental findings are considered. The findings are also discussed in the context of results that suggest that the timing of breast cancer surgery during the menstrual cycle in premenopausal women may affect probability of survival, and possible implications of the findings for tumor dormancy are discussed.