Current status of intensity-modulated radiation therapy for prostate cancer: History, clinical results and future directions.

External beam radiotherapy has changed dramatically over several decades with the improvement of computer hardware and software, and machinery developments. Intensity-modulated radiation therapy is the most sophisticated technique for all cancer treatment with radiation therapy, and is widely disseminated and available for daily use in many countries. Several retrospective and prospective studies have shown that intensity-modulated radiation therapy reduces the radiation dose in the organs at risk with diminished rates of acute and late toxicity, even with higher doses (>74 Gy). An important technique for the clinical use of intensity-modulated radiation therapy is image-guided radiation therapy. The clinical benefit for prostate image-guided radiation therapy has been assessed by comparing the outcomes of patients with either the image-guided radiation therapy or non-image-guided radiation therapy technique. These studies have shown that image-guided radiation therapy significantly decreases acute and late rectal and bladder toxicities. Randomized trials and meta-analysis have shown that higher doses result in better biochemical control. More recently, hypofractionated radiation therapy comparing hypofractionated radiation therapy versus conventional fractionated radiation therapy have shown that hypofractionated radiation therapy produces biochemical control and toxicity rated similar to those produced by conventional fractionated radiation therapy. The clinical use of ultrahypofractionated radiation therapy and simultaneous integrated boost technique is necessary to evaluate its further safety and benefits. Intensity-modulated radiation therapy is also widely accepted in the field of salvage therapy and for the patients with distant oligometastases. The purpose of the present review is to summarize the history of intensity-modulated radiation therapy, new techniques for intensity-modulated radiation therapy, hypofractionation and future directions for prostate cancer.