Large-scale dose evaluation of deep learning organ contours in head-and-neck radiotherapy by leveraging existing plans

Background and purpose

Retrospective dose evaluation for organ-at-risk auto-contours has previously used small cohorts due to additional manual effort required for treatment planning on auto-contours. We aimed to do this at large scale, by a) proposing and assessing an automated plan optimization workflow that used existing clinical plan parameters and b) using it for head-and-neck auto-contour dose evaluation.

Materials and methods

Our automated workflow emulated our clinic’s treatment planning protocol and reused existing clinical plan optimization parameters. This workflow recreated the original clinical plan ($P_{\mathrm{OG}}$) with manual contours ($P_{\mathrm{MC}}$) and evaluated the dose effect ($P_{\mathrm{OG}}-P_{\mathrm{MC}}$) on 70 photon and 30 proton plans of head-and-neck patients. As a use-case, the same workflow (and parameters) created a plan using auto-contours ($P_{\mathrm{AC}}$) of eight head-and-neck organs-at-risk from a commercial tool and evaluated their dose effect ($P_{\mathrm{MC}}-P_{\mathrm{AC}}$).

Results

For plan recreation ($P_{\mathrm{OG}}-P_{\mathrm{MC}}$), our workflow had a median impact of 1.0% and 1.5% across dose metrics of auto-contours, for photon and proton respectively. Computer time of automated planning was 25% (photon) and 42% (proton) of manual planning time. For auto-contour evaluation ($P_{\mathrm{MC}}-P_{\mathrm{AC}}$), we noticed an impact of 2.0% and 2.6% for photon and proton radiotherapy. All evaluations had a median $\Delta$NTCP (Normal Tissue Complication Probability) less than 0.3%.

Conclusions

The plan replication capability of our automated program provides a blueprint for other clinics to perform auto-contour dose evaluation with large patient cohorts. Finally, despite geometric differences, auto-contours had a minimal median dose impact, hence inspiring confidence in their utility and facilitating their clinical adoption.