Tumour growth and cancer therapy

Tumour growth is the result of a complex balance between cell production and cell loss. The different rate of growth in different tumours depends on the extent to which this balance is tipped towards cell production. In some tumours most cells that are born contribute to the net growth, especially in fast-growing sarcomas. In other tumours very few of the tumour cells that are produced contribute to net growth, for example in slow-growing carcinomas. The kinetics of tumour cells is greatly influenced by the proliferation rate and pattern of branching of the capillary network supplying the tumour. These also influence the response to chemotherapy and to radiotherapy. In chemotherapy the kinetics of the tumour relative to the most rapidly growing cells anywhere in the body influences the potential therapeutic benefit that can be achieved. Radiotherapy depends on the relative kinetics and sensitivities of tumour and local normal tissues within the beam, including the tissue of origin.