PV QA 3 - Poster Viewing Q&A 3
Purpose/Objective(s): For locally-advanced non-small cell lung cancer (NSCLC), intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) remained as mainstay treatment due to large irradiation field. In this study, we aimed to compare the dosimetric difference and efficiency between jaw tracking technique (JTT) and static jaw technique (SJT) using the full-arc VMAT, partial-arc VMAT and IMRT for locally advanced NSCLC.
Materials/Methods: Jaw tracking technique and static jaw technique combined with full-arc VMAT, partial-arc VMAT, and IMRT were used respectively to develop treatment plans for 11 patients with locally advanced NSCLC scheduled for definitive radiotherapy with a total dose over 50 Gy. Target dose coverage aimed to cover CTV with 100% and PTV with at least 95% of the prescribed dose. The main OARs considered were lung, spinal cord and esophagus. Six treatment plans were built-up for each patient, and all plans were performed with the same objectives and constraint while plan optimization. After plan optimization, we retrieved dosimetric indexes, including conformal index (CI), homogeneous index (HI), V5, V10, V20, V30 and Dmax based on dose-volume histograms (DVH) and documented expected beam on time and the monitor units (MUs) of each plan.
Results: For all patients, six treatment plans met the clinical requirements and revealed acceptable and comparable target dose coverage (CI: 0.97-1.03; HI: 1.09-1.12). As for OARs dose exposure, JTT revealed significant dose reduction compared with SJT regardless of therapy, especially in ipsilateral lung sparing. Second, among partial-arc VMAT, full-arc VMAT, and IMRT, partial-arc VMAT showed an advantage in decreased V20 in contralateral lung and decreased V35 in esophagus (21-24% reduction); full-arc VMAT revealed decreased V30 in heart (37-46% reduction). Both partial-arc VMAT and full-arc VMAT showed decreased Dmax of spinal cord (4-11% reduction), shorter treatment time (49-68% reduction), and less MUs (60-66% reduction).
Conclusion: For locally advanced NSCLC, jaw tracking technique showed superior OARs sparing than static jaw technique. Besides, both partial-arc VMAT and full-arc VMAT provided conformal dose distribution to target, decreased scattering dose over OARs and shorter treatment time compared with IMRT. Overall, a combination of jaw tracking technique and VMAT may contribute to efficient and effective treatment plan.
The asset you are trying to access is locked. Please enter your access key to unlock.