Late effects of radiotherapy in the treatment of breast cancer.

Late effects after radiotherapy for breast cancer include radiation induced malignancy and changes in irradiated tissues leading to e.g. edema of the arm, decreased mobility of the shoulder joint, brachial plexus neuropathy, pulmonary fibrosis, telangiectasia or atrophic ulceration of the skin. While radiation-induced malignancy depends on the volume of tissue irradiated and the total dose, other late effects are also fractionation dependent. Several reports have shown increased rates of such late effects after changes of the fractionation schedule which should be isoeffective according to the mathematical models commonly used to predict early effects. Although knowledge of the relation between total dose, number of fractions and radiation effects in late responding tissues has increased, extrapolations from the models should be used cautiously. The dose-response curve seems to be steeper for late effects than for tumour control. The possibility of late effects should be included in the decision as to when and how to treat breast cancer with radiotherapy.