Principles of chemotherapy and radiotherapy

Radiotherapy and chemotherapy are both widely used in the management of gynaecological malignancy. The reasons why tumours are destroyed and normal tissues recover after radiotherapy are complex and thought to be due to differences in intrinsic radiosensitivity and the ability to repair and repopulate between normal and malignant tissue. Some tumours are hypoxic, which makes them radioresistant. Most radiotherapy treatments are carried out using a linear accelerator, which produces photons or high energy x-rays that are ‘skin sparing’ and can treat deep-seated tumours. Brachytherapy (short distance treatment) with implanted or internal radiation sources can also be used, and indeed is an essential part of the radical radiotherapy for cervical carcinoma.Chemotherapeutic agents currently in use are cytotoxic and affect both normal and malignant cells. Side-effects include bone marrow suppression, nausea and vomiting, epilation, renal, cardiac and neurotoxicity. Ideally, agents with different mechanisms of action should be given in combination to overcome potential drug resistance. Multiple drugs should have differing patterns of toxicity so the highest tolerable doses can be given. Chemotherapy can also be given concurrently with radiotherapy to enhance the therapeutic effect. Newer biological agents are increasingly being used in the treatment of cancers. As most gynaecological chemotherapy treatments are palliative, patients should be selected with great care; the possible benefits of the treatment must be balanced against the risk of side-effects.