Numerous technological advances over the past several decades in radiation oncology have allowed a stepwise progression toward the delivery of increasingly conformal radiation treatments. These improvements have subsequently resulted in superior patient outcomes and widening of the therapeutic ratio. The rationale underlying radiotherapy delivery is based on the “as low as reasonably achievable” (ALARA) principle, which dictates that, above all else, the goal of treatment is to deliver a meaningful and optimal dose to the target volume while concomitantly delivering as little dose as possible to normal surrounding tissues—in other words, to deliver the most conformal plan achievable to maximize tumor control while minimizing toxicity to normal tissues from excess radiation dose.

During the evolution from two-dimensional (2D) radiotherapy to 3D conformal radiotherapy (3D-CRT) to intensity-modulated radiation therapy (IMRT), the adoption of novel technologies in radiation oncology has involved the acquisition of new hardware, software, and clinical workflows, many of which have also involved increases in staff time, expenses to the treatment facility, and costs of treatment. Even so, these advancements in radiation therapy technology have been nearly universally adopted in the United States and are generally reimbursed by insurance carriers even though exceedingly few randomized trials or high-level data exist to demonstrate the superiority over older technologies. In the case of IMRT, only a handful of prospective randomized trials have ever shown benefits in toxicity or quality of life from use of this modality over 3D-CRT1,2 and data on survival benefits from IMRT are still lacking. Instead, the wider incorporation of advanced technologies has been based on the first principles of radiotherapy: striving to reduce the dose to nontarget normal tissues to avoid toxicity while delivering a more optimal dose to target areas to improve tumor control.