Monte Carlo simulations will change the way we treat patients with proton beams today.

Within the past two decades, the evolution of Monte Carlo simulation tools, coupled with our better understanding of physics processes and computer technology has enabled accurate and efficient prediction of particle interactions with tissue. Monte Carlo simulations have now been applied for routine clinical applications. This commentary outlines how simulations have the potential to change clinical practice particularly in proton therapy. Specifically, Monte Carlo simulations will impact treatment outcome analysis, reduce treatment volumes and help understand proton-induced radiation biology.