MO‐A‐137‐10: Evaluation of A GPU‐Based In‐House Automatic Re‐Planning System for Adaptive Radiotherapy Re‐Planning for Head and Neck Cancer

Purpose: To evaluate the feasibility and quality of adaptive radiation therapy (ART) re‐planning for head‐and‐neck (H/N) cancer using SCORE, an in‐house graphics processing unit (GPU)‐based automatic re‐planning system. Methods: Our in‐house automatic re‐planning system SCORE utilizes GPU computational efficiency to register CT images, deform contours, and re‐optimize treatment plans. We used SCORE to generate two re‐plans for ten previously‐treated bilateral H/N patients who were re‐planned during the course of their IMRT treatment. The first plan (AUTOCONTOURAUTOPLAN) employed the full automatic replanning procedure while the second plan (AUTOPLAN) used the approved manually re‐contoured structures from the clinically treated re‐plan for SCORE optimization. To evaluate SCORE performance in terms of plan quality, both with and without human intervention in the contouring process, we compared the two SCORE plans to the clinically‐delivered plan. Results: We compared dose volume histograms along with max/mean organ dose for each plan to the clinically treated re‐plan. For AUTOCONTOURAUTOPLAN, we cast the manually re‐contoured structures over the dose distribution to be able to compare dose on the same contours. Averaging over 10 patients, AUTOPLANAUTOCONTOUR reduced max brainstem, max cord, mean left parotid, and mean right parotid relative dose by 17.2(SD:12.4)%, 3.5(SD:6.3)%, 9.1(SD:6.5)%, and 9.6(SD:6.4)%, respectively, but also decreased high dose PTV coverage with a relative dose difference of ‐ 10.3(SD:3.83)% at 99% of the volume. AUTOPLAN reduced max brainstem, max cord, mean left parotid, and mean right parotid relative dose by 22.7(SD:9.2)%, 10.8(SD:7.8)%, 9.1(SD:8.0)%, and 5.5(SD:5.8)%, respectively, while the high‐dose PTV at 99% of volume increased by 0.1(SD:1.6)% and volume greater than 110% of the dose increased by 5.7(SD:6.5)%. Conclusion: We found the automated AUTOCONTOURAUTOPLAN demonstrated organ sparing improvements, but decreased PTV coverage. The partially automated AUTOPLAN showed significant dosimetric improvements in terms of both organ sparing and PTV coverage but yielded plans that may be considered clinically hot.