SU-E-T-568: Individualize the Treatment Plan with Anatomic Optimization for Lung Tumor Stereotactic Ablative Radiotherapy

Abstract

Purpose: To demonstrate that an individualized anatomical optimized approach for each patient undergoing stereotactic ablative radiotherapy (SABR) for lung cancer will Result in a superior dosimetric treatment plan. Methods: Eleven patients were received 4DCT with both natural and extreme tidal volume breathing. The original treatments were planned on either natural end exhale (NEE) or deep inspiration breath hold (DIBH) CT image. For re-plan, all structures were deformed from the planned CT image to the opposite CT image. The dose was recalculated to meet the physician constraints. The dosimetric impact of the anatomically optimized approach was evaluated and compared for both plans. Results: From the 11 patients that were analyzed in this study, 8 patients were planned and treated on DIBH, whereas 3 patients were planned and treated on NEE. Two patients treated on NEE had a lower maximum dose to the great vessels compared to the plan on DIBH. One patient treated on DIBH had a higher dose to the great vessels compared to the plan on NEE, indicating that this patient would be benefited from the treatment on NEE. The dose reduction is due to the increased separation between the target and the OAR from 1.61cm to 2.77cm in average. Conclusion: In summary, anatomic optimization favored NEE rather than DIBH in 27% of patients. This study demonstrates proof of principle that an individualized anatomically optimized approach is feasible and could lead to lower doses to nearby organs at risk. While the majority of patients are benefited from treatment on DIBH, our data suggests that in order to maximize the efficacy of the treatment and minimize the toxicity to the nearby tissue, the separation between target and OAR should be evaluated individually for each patient. Funded through departmental Master Reseacrh Agreement with Varian Medical Systems, Inc