of cytotoxic therapy

Figure 19.1) describes the natural history of tumour growth. By the time that a tumour is clinically detectable, the majority of its growth has already occurred. In the early exponential phase of growth, the rates of tumour cell growth and tumour cell loss are proportional to the tumour cell burden at any point. Since most anticancer agents are more toxic to proliferating cells and most tumours are in a relatively slow phase of growth when diagnosed (i.e. they lie high and towards the plateau of the Gompertzian growth curve), it explains the limited effectiveness of chemotherapy for many cancers. The reason for tumour cytoreduction (e.g. by surgery) before chemotherapy is to bring the tumour to a lower point on the growth curve when the growth fraction of the tumour rises. The concept of moving the tumour down the Gompertzian curve underpins the rationale of adjuvant chemotherapy.