Current concepts in metastasis.

Metastasis remains an important clinical problem.In gastrointestinal cancers it is the single most important determinant of death.The incidence of metastatic disease from colorectal cancer at presentation is 25%.'Even after curative surgical resection the five year sur- vival rate is no more than 50% with an overall five year survival rate for colorectal cancer of 25-30%.2 3 The presence of liver metastases confers a median survival of only six months,4 figures that have essentially remained unchanged for over 40 years.At present our armamentarium against colorectal metastasis is weak.Surgery is limited to a fraction of cases and the alternative is systemic or regional chemotherapy.Results from such treatments are poor, only about 15-20% of tumours responding to systemic chemotherapy with mar- ginal benefits in terms of survival.5Such dismal figures lead to the conclusion that perhaps novel approaches are required in the prevention, early diagnosis, and treatment of liver metastasis.The questions that therefore arise are does modern science have anything to offer towards this problem and where is current research lead- ing from a clinical perspective.A detailed description of the metastatic process is beyond the scope of this article.The role of oncogenes and tumour suppressor genes in the neoplastic process has been previously described and will not be referred to either.Here, we highlight two areas of current research in cell biology, namely, adhesion molecules and a group of matrix degrading enzymes, the metalloproteinases, and their roles in the progression and metastasis of tumours.