2 - Invasion and metastasis

Summary

The significance of metastases is that they “form an ineluctable hindrance to successful therapy.”

Alton Ochsner and M. DeBakey 1942

The detection of metastases constitutes decisive evidence for categorizing a proliferating primary lesion, previously of uncertain potential, as neoplastic and “malignant,” and the phenomenon is a topic of unparalleled importance in cancer medicine and biology.

D. Tarin 1992

Introduction

Ochsner and DeBakey's use of the terms “ineluctable hindrance” in describing the effects of metastasis on cancer therapy, written well over a half century ago, is essentially valid today. Metastasis is feared by both patient and physician and that fear is not without merit. Metastases remain the principal cause of death by cancer. But, changes in the understanding of invasion and metastasis may soon necessitate reconsideration of this dismal prospect for cancer patients. The phenomena of cancer invasion and metastasis, with its many steps forming a “cascade,” have remained unchanged. However, the molecular events of metastasis, in particular metastasis suppressor genes and their expression, are now recognized and their understanding is evolving. Implicit with that understanding is the possibility, indeed the likelihood, of chemotherapeutic agents that specifically target metastasis suppressor genes. Understanding invasion and metastasis is critically important to the understanding of the pathogenesis of cancer.

It has been said that cancer is infrequently a localized disease. This is because of the propensity of malignant neoplasms to disseminate early in the disease and to grow as secondary tumors in the body of the host.