CTing STARs.

Top Line: Where are we on adaptive radiation using CT rather than MRI?

The Study: This prospective pilot study evaluated the feasibility of adaptive treatment planning using pre-treatment cone-beam (CB) CT for 8 patients receiving 50 Gy in 5 fractions for abdominal oligometastases. Important to note is that this was an in silico trial, so patients received treatment based on their standard simulation CT. The pre-treatment CBCTs for each fraction were used to generate CBCT-based adaptive plans. This was all done on the Varian ETHOS platform. Treatment deliveries resulted in stomach and or bowel doses exceeding constraints in 30/40 (75%) fractions when based on simulation CT versus only 2/40 (5%) fraction when adapted per daily imaging. What’s more, adaptive plans also improved target coverage for the majority of fractions. The downside? An increase in daily treatment times by a median of 23 minutes (range: 11-47 minutes) with, as of yet, no proven clinical benefit.

TBL: Daily CBCTs may be capable of generating high-quality adaptive treatment plans for SBRT for abdominal oligometastases. | Schiff, Int J Radiat Oncol Biol Phys 2022