Radiotherapy for breast cancer in the 21st Century.

Radiotherapy has undergone significant technological advances during the last 20 years, although their use in breast cancer was relatively limited until recently. The major recent changes in the use of radiotherapy for breast cancer have been the following: the establishment of partial breast irradiation (PBI) as an option for therapy in early stage disease; the revival of hypofractionated therapies for breast only therapy; the clearer definition of the role of post-mastectomy irradiation; and the continuing investigation as to which patients having conservative surgery do not need radiation therapy. Intensity-modulated radiotherapy is still not widely accepted to be medically necessary in breast cancer, but ongoing studies may demonstrate that it will prove to be useful in treating node-positive breast cancer when wide-field nodal targets need to be included in the treatment volume. Image-guided radiotherapy will prove to be necessary for PBI by external beam to keep the irradiated treatment volumes within long-term tolerance. The optimum dose and delivery schedule for PBI is yet to be finalized. Overall, the local control rates for all breast cancer treatment scenarios are generally good, and therefore, the emphasis is now on maintaining local control while reducing toxicities from treatment. The long-term risks of breast cancer radiotherapy on subsequent cancer induction are subject to ongoing studies. Biological enhancement of the effect of radiotherapy could allow dose reduction, with presumed reductions in the toxicity of treatment. In conclusion, breast cancer radiotherapy has much to understand and optimize in the 21st Century.