Volumetric modulated arc therapy for delivery of hypofractionated stereotactic lung radiotherapy: A dosimetric and treatment efficiency analysis

• Published in: Radiotherapy and oncology Vol. 95; no. 2; pp. 153 - 157
• Main Authors: McGrath, Samuel D, Matuszak, Martha M, Yan, Di, Kestin, Larry L, Martinez, Alvaro A, Grills, Inga S
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01.05.2010
• Subjects: Carcinoma, Non-Small-Cell Lung - radiotherapy; Dose Fractionation; Extracranial stereotactic radiotherapy; Female; Hematology, Oncology and Palliative Medicine; Humans; Hypofractionation; Lung cancer; Lung Neoplasms - radiotherapy; Male; Neoplasm Staging; Radiotherapy Planning, Computer-Assisted - instrumentation; Radiotherapy Planning, Computer-Assisted - methods; Radiotherapy, Intensity-Modulated - methods; Treatment Outcome; VMAT; Hypofractionation; VMAT; Extracranial stereotactic radiotherapy; Lung cancer
• ISSN: 0167-8140; 1879-0887
• DOI: 10.1016/j.radonc.2009.12.039

Abstract Purpose/objective(s) Volumetric modulated arc therapy (VMAT) allows for intensity-modulated radiation delivery during gantry rotation with dynamic MLC motion, variable dose rates and gantry speed modulation. We compared VMAT plans with 3D-CRT for hypofractionated lung radiotherapy. Materials/methods Twenty-one 3D-CRT plans for Stage IA lung cancer previously treated stereotactically were selected. VMAT plans were generated by optimizing machine aperture shape and radiation intensity at 10° intervals. A partial arc range of 180° was manually selected to coincide with tumor location. The arc was resampled down to 5° intervals to ensure dose calculation accuracy. Identical planning objectives were used for VMAT/3D-CRT. Parameters assessed included dose to PTV and organs-at-risk (OAR), monitor units, and multiple conformity and homogeneity indices. Plans were delivered to a phantom for time comparison. Results Lung V20/12.5/10/5 were less with VMAT (relative reduction 4.5%, p = .02; 3.2%, p = .01; 2.6%, p = .01; 4.2%, p = .03, respectively). Mean/maximum-doses to PTV, dose to additional OARs, 95% isodose line conformity, and target volume homogeneity were equivalent. VMAT improved conformity at both the 80% (1.87 vs. 1.93, p = .08) and 50% isodose lines (5.19 vs. 5.65, p = .01). Treatment times were reduced significantly with VMAT (mean 6.1 vs. 11.9 min, p < .01). Conclusions Single arc VMAT planning achieves highly conformal dose distributions while controlling dose to critical structures, including significant reduction in lung dose volume parameters. Employing a VMAT technique decreases treatment times by 37–63%, reducing the chance of error introduced by intrafraction variation. The quality and efficiency of VMAT is ideally suited for stereotactic lung radiotherapy delivery.