Collateral damage.

What if you could give 24 Gy x 1 anywhere in the body? That’s right, you’d kill a lot of cancer. The problem is that oligometastatic cancer often involves serial organs for which such a dose is high risk. This paper posits that delivery of a high, ablative single fraction dose to a sub-volume of tumor while sparing adjacent critical organs may set off a chain-reaction of radiobiological bystander effects sufficient to kill the under-dosed tumor cells. They call it perfusion-modulated dose sculpting (PMDS), and it’s a biological effect not seen when fractionated SBRT is used. Tumor control with PMDS was comparable to complete target coverage with 24 Gy x 1, although a key threshold for efficacy was that 60% or more of the PTV had to be included in the high-dose PTV. | Greco, Int J Radiat Oncol Biol Phys 2020