hematology and oncology
Systemic Cancer Therapy
Introduction
Systemic cancer therapy includes chemotherapy (ie, conventional or cytotoxic chemotherapy), hormone therapy, targeted therapy, and immune therapy (see also Overview of Cancer Therapy ). The number of approved cancer therapies is increasing rapidly. The The ideal drug would target only cancer cells and have no adverse effects on normal cells. Although older chemotherapeutic drugs are often toxic to normal cells, advances in genetics and cellular and molecular biology have led to development of more selective drugs. Most cancer drugs are given systemically, usually intravenously or subcutaneously, but some are given by mouth. Frequent dosing for extended periods may necessitate intravenous implanted access devices. Resistance to cancer drugsis common. Mechanisms include Over-expression of target genes Mutation of target genes Development of alternative drug metabolic pathways Drug inactivation by cancer cells Defective apoptosis in cancer cells Loss of receptors for hormones For chemotherapy drugs, one of the best characterized resistance mechanisms is overexpression ofMDR1, a cell membrane transporter that causes efflux of certain drugs (eg, vinca alkaloids, taxanes, anthracyclines). Attempts to alterMDR1function and prevent drug resistance have been unsuccessful. 