High energy Xrays are used to induce genetic damage in cancer cells, resulting in their eventual elimination by body defense mechanisms.
This forms the basis of radiotherapy, which is the most important method of nonsurgical treatment of localised cancers. Old generation Cobalt machines were effective, but resulted in significant toxicity and morbidity to the patient. Nowadays they have more or less been replaced by new generation Linear Accelerators that allow more precise treatment delivery with fewer side effects. This makes radiation a still more attractive option in patients who are not willing for; or due to medical reasons, unfit for surgery.
Other refinements that have revolutionized radiation treatment is three-dimensional planning, dose painting and image-guided radiotherapy have resulted in lesser toxicity and more efficacy by sparing of critical structures, and by correcting issues related to patient movement, respiration or tumor shrinkage during treatment.
Yet another advancement is in the field of brachytherapy where radioactive materials may be placed within the tumor to deliver continuous radiation with least amount of side effects to normal tissues. Precision techniques and image guidance has also allowed the focussed use of radiation beams as gamma knife to treat tumors within critical and surgically inaccesible locations.
