Table 1.

Comparisons of and indications for intensity-modulated radiotherapy–volumetric modulated arc radiotherapy (IMRT-VMAT), double-scattering proton therapy (DSPT), and intensity-modulated proton therapy (IMPT).

Technique	Advantages	Disadvantages	Clinical scenarios indicated
IMRT-VMAT	High conformality of the prescription isodose lines around the target; robust and consistent for patient anatomy and patient motion	Increased dose to surrounding organs at risk in the low- to medium-dose range (0–50 GyRBE); potentially long beam-exposure times requiring intrafraction image guidance and position corrections	Localized prostate cancer; salvage or adjuvant prostate bed radiation therapy; elective pelvic node irradiation
DSPT	Reduced dose to surrounding organs at risk within the low- to medium-dose range (0–50 GyRBE); fast delivery times for targets without complex shapes; smoothing and smearing of dose with a compensator allows for robust proton therapy delivery for patient anatomy and motion	Low conformality of prescription isodose lines for complex targets; long treatment times for targets with complex shapes	Localized prostate cancer; salvage or adjuvant prostate bed radiation therapy
IMPT	High conformality with prescription isodose lines; reduced dose to surrounding organs at risk within the low- to medium-dose range (0–50 GyRBE)	Plan robustness for patient motion and anatomy can be challenging for targets with increased motion or significant changes in density or long beam delivery times; potentially long delivery times depending on spot scanning speed	Localized prostate cancer; salvage or adjuvant prostate bed radiation therapy; elective pelvic node radiation therapy; high-dose pelvic node radiation therapy delivered for patients with pelvic node adenopathy