Principles of chemotherapy

Cells in tumours do not all grow and divide at the same rate. Initially, growth is exponential that is each cell divides to produce two, which then divide to produce four and so on. As a tumour gets larger growth slows down, partly because it outgrows its blood supply and partly because not all cells in the tumour divide continuously. 

Cells in a solid tumour can be in three different states  

Cells that are dividing are the best targets for chemotherapy, but they may only represent 5% of the total of tumour mass. Cells that can no longer divide do not present a problem, but cells that are resting are often resistant to cytotoxic drugs and can re-enter the cell cycle after a course of chemotherapy. 

Drugs used to treat cancer act on some stage in the cell cycle, either on DNA synthesis or spindle formation or cause damage to preformed DNA. Phase-specific drugs act at a particular point in the cycle, usually S phase or M phase. Phase-non-specific drugs are cytotoxic at any point in the cell cycle and may be toxic to cancer cells in the 

However, most cancer drugs are effective in the S phase of dividing cells, preventing normal DNA synthesis so that the cells go into apoptosis. Drug therapy aims to prevent cell division or cause cell death in the tumour without damaging normal healthy cells. Cancer cells are similar to normal cells, so this is often impossible and explains many of the side effects of chemotherapy. 

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Thus, at the end of this period, the scientific principles of chemotherapy. 

The antiviral strategies discussed earlier as well as all antiviral drugs available to date are based on the principles of conventional chemotherapy. However, recent discoveries and developments in molecular biology have opened perspectives for alternative approaches of intervention. 

Biology Complicates the Delivery of Radiation Biology Also Complicates the Delivery of Chemotherapy Principles Guiding the Integration of Chemoradiation Ideal Radiosensitizer ... 

Katzung PHARMACOLOGY, 9e > Section VIII. Chemotherapeutic Drugs > Chapter 52. Basic Principles of Antiparasitic Chemotherapy > ... 

The origins of antiviral therapies can be traced to the early 1950s, when sulfonamide antibiotics were tested for activity against poxviruses using mice infected with vaccinia (1). A decade of work at the Wellcome laboratories culminated in the development of methisazone, which was introduced in 1960 for the prophylaxis of smallpox (see Scheme 1). Notable success in the smallpox epidemic in Madras in 1963 demonstrated the value of this compound, but vaccines introduced soon after led to eradication of the disease and made the compound redundant. However, the principle that chemotherapy was effective for treating antiviral diseases had been demonstrated. 

Carmichael J (1992) The principles of cancer chemotherapy. In Grahame-Smith DG, Aronson JK (eds) Oxford textbook of clinical pharmacology, 2nd edn. Oxford University Press, Oxford, 505-515... 

The study of tumor growth forms the foundation for many of the basic principles of modem cancer chemotherapy. The growth of most tumors is illustrated by the Gompertzian tumor growth curve (Fig. 124-5). Gompertz was a German insurance actuary who described the relationship between age and expected death. This mathematical model also approximates tumor-cell proliferation. In the... 

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