Radiotherapy is utilised in the treatment of up to 50% of patients with solid tumours. Along with chemotherapy and surgery it makes up the triad of major anticancer therapies. 

However, the effective dose of radiotherapy that can be delivered is often limited either by toxicity to the surrounding normal tissue or resistance of the tumour.  Significant research has been conducted examining ways of minimising this toxicity or overcoming resistance.  These have included not only advances in administration techniques but also the use of combined modality treatments. 

The idea of using chemical agents in combination with radiotherapy has been explored for many years.  The use of agents that sensitise tumour cells to radiotherapy and increase radiotherapy-induced kill is common practice in some malignancies, including lung and head and neck cancers.

Three properties of tumours have been shown to influence response to radiotherapy: 1) The extent of hypoxia present; 2) The ability of surviving cells to repopulate; and 3) The intrinsic radioresistance of the tumour cells.  The addition or incorporation of either conventional or novel agents into treatment regimes is designed to overcome these issues.

The rationale and evidence for current combined chemoradiation protocols will be examined, as well as how advances in our understanding of the molecular biology of tumours has resulted in increased treatment options.