What is the best way to radiate the prostate in 2016? 
Prostate cancer treatment with definitive radiation therapy (RT) has evolved dramatically in the past 2 decades.  From the initial 2-dimensional planning using X-rays, advances in technology led to 3-dimensional conformal RT, which used computerized tomography-based planning.  This has allowed delivery of higher doses of radiation to the prostate while reducing dose to the surrounding organs, resulting in improved cancer control.  Today, intensity-modulated RT (IMRT) is considered standard, where radiation beams of different shapes and intensities can be delivered from a wide range of angles, thus further decreasing doses to normal organs and likely reducing treatment-related toxicity.  In addition, image guidance ascertains the location of the prostate before daily treatment delivery.  Brachytherapy is the placement of radioactive seeds directly in the prostate, and has a long track record as a monotherapy for low-risk prostate cancer patients with excellent long-term cancer control and quality of life outcomes.  Recent studies including several randomized trials support the use of brachytherapy in combination with external beam RT for higher-risk patients.  RT for prostate cancer continues to evolve.  Proton therapy has a theoretical advantage over photons as it deposits most of the dose at a prescribed depth with a rapid dose fall-off thereafter; therefore it reduces some doses delivered to the bladder and rectum.  Prospective studies have shown the safety and efficacy of proton therapy for prostate cancer, but whether it leads to improved patient outcomes compared to IMRT is unknown.  Hypofractionated RT delivers a larger dose of daily radiation compared to conventional IMRT, and thus reduces the overall treatment time and possibly cost.  An extreme form of hypofractionation is stereotactic body radiation therapy where highly precise radiation is used and treatment is completed in a total of 4 to 5 sessions.  These techniques take advantage of the biological characteristic of prostate cancer, which is more sensitive to larger radiation doses per fraction, and therefore could be more effective than conventional IMRT.  Multiple randomized trials have demonstrated noninferiority of moderately hypofractionated RT compared to conventional fractionation.  There is also a growing body of data demonstrating the safety and efficacy of stereotactic body radiation therapy for low- and intermediate-risk prostate cancer.