Exploring a hybrid workflow on current adaptive radiotherapy systems

We introduce a novel hybrid workflow in adaptive radiotherapy that combines traditional image guidance capabilities with an AI-based adaptive radiotherapy platform.

The Ethos adaptive radiotherapy system currently lacks the capability for manual couch shifts at the time of treatment delivery. It offers two options: 1) a scheduled (non-adaptive) plan and 2) a daily reoptimized adaptive plan. Our hybrid workflow simulates optimal couch shifts applied to the scheduled plan to maximize target dose and minimize dose to critical organs while reducing patient time on the couch. We evaluated five prostate patients previously treated on the Ethos system. For each patient, data included one reference plan, 20 scheduled plans, and 20 adapted plans. Dose-volume statistics of PTV and organs-at-risk were compared among the scheduled, hybrid, and adapted plans.

The optimal couch shifts determined using the hybrid workflow ranged from -7 to 10 mm and increased the PTV coverage by up to 21.0 % compared with the scheduled plan. Adapted plans provided the highest target coverage, with a maximum improvement of 16.4 % over the hybrid workflow plans. Rectal and bladder sparing were similar between our hybrid workflow and the scheduled plan. However, compared with the adapted plan, the hybrid workflow reduced rectal V45 in 4/5 patients and bladder V45 in 2/5 patients, with maximum reductions of 9.4 % and 5.7 %, respectively.

This study suggests that incorporating manual couch shifts into adaptive radiotherapy could substantially enhance treatment quality and influence the decision when choosing between an adapted and non-adapted plan.