Anatomic optimization of lung tumor stereotactic ablative radiation therapy

Purpose: The purpose of this study was to demonstrate that anatomic optimization through selection of the degree of breath hold that yields the largest separation between the target and nearby organ at risk could result in dosimetrically superior treatment plans. Methods and materials: Thirty patients with 41 plans were included in this planned secondary analysis of a prospective trial. Fifteen planswere created for treatment with use of natural end exhale (NEE), and 26 plans used deep inspiration breath hold (DIBH). To evaluate whether the original plan was dosimetrically optimal, we replanned treatment using the opposite respiratory state with the same beam configuration as the original plan. A treatment plan was deemed superior if it met protocol constraints when the other did not. If both plans met or violated the constraints, the plans were deemed equivalent. Results: Of the 26 plans originally planned with DIBH and replanned with NEE, 3 plans were dosimetrically superior with NEE, 1 plan was dosimetrically superior with DIBH, and 22 plans were dosimetrically equivalent. Of the 15 plans originally planned with NEE, 4 plans were dosimetrically superior with NEE, 2 plans were dosimetrically superior with DIBH, and 9 plans were dosimetrically equivalent. Conclusions: For 10 of 41 plans, planning with 1 respiratory state was superior. To obtain uniformly optimal plans, individual anatomic optimization would be needed. (C) 2015 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.