What Is Cancer?: 2 Cancer Metastasis

Metastases are tumor foci growing at distant sites from the original tumors. In many cancers, metastases cause inconvenience and pain for the patients and are often responsible for therapeutic failures. Ninety percent of cancer-related deaths are known to be due to metastasis. Therefore, it is often remarked that if metastasis is conquered, then cancer can be conquered. Metastasis, present at the time of the initial diagnosis or discovered during the therapy, significantly changes how the disease is dealt with by clinicians and their patients. Despite advances in the understanding and treatment of primary tumors, the treatment of metastatic cancer remains a big challenge. The purpose of this chapter is to outline the biology of cancer metastasis in a broad context and to discuss why, how, when, and where metastases occur. In this chapter, the readers will understand the biological basis of metastasis as a process having both specific and stochastic elements reminiscent of embryogenesis, morphogenesis, and even evolution, and as an inefficient result of many consecutive processes taking place throughout all the stages of cancer. Based on these clinical and biological features, it is true that cancer is potentially intractable because it acquires metastatic capability. Thus, cancer is malignant due to metastasis.