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Neurosurgery:
doi: 10.1227/NEU.0000000000000448
RESEARCH - HUMAN - CLINICAL STUDIES: PDF Only

Comparison of Plan Quality and Delivery Time between Volumetric Arc Therapy (RapidArc) and Gamma Knife Radiosurgery for Multiple Cranial Metastases.

Thomas, Evan M M.S.; Popple, Richard A Ph.D.; Wu, Xingen Ph.D.; Clark, Grant M M.D.; Markert, James M M.D.; Guthrie, Barton L M.D.; Yuan, Yu Ph.D; Dobelbower, Michael C M.D., Ph.D.; Spencer, Sharon A M.D.; Fiveash, John B M.D.

Published Ahead-of-Print
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Abstract

Background: Volumetric modulated arc therapy (VMAT) has been shown feasible for radiosurgical treatment of multiple cranial lesions with a single isocenter.

Objective: To investigate whether equivalent radiosurgical plan quality and reduced delivery time could be achieved in VMAT for patients with multiple intracranial targets previously treated with Gamma Knife (GK) radiosurgery.

Methods: We identified 28 Gamma Knife treatments of multiple metastases. These were replanned for multi-arc (MA) and single-arc (SA), single-isocenter VMAT (RapidArc) in Eclipse. The prescription for all targets was standardized to 18 Gy. Each plan was normalized for 100% prescription dose to 99-100% of target volume. Plan quality was analyzed by target conformity (RTOG, Paddick CI), dose fall-off (area under DVH curve), as well as the V4.5, V9, V12, and V18 isodose volumes. Other endpoints included beam-on and treatment time.

Results: Compared to Gamma Knife, multi-arc VMAT improved median plan conformity (CIVMAT = 1.14, CIGK = 1.65; p<0.001) with no significant difference in median dose fall-off (p=0.269), 12Gy isodose volume (p=0.500), or low isodose spill (p=0.49). Multi-arc VMAT plans were associated with markedly reduced treatment time. A predictive model of the 12Gy isodose volume as a function of tumor number and volume was also developed.

Conclusion: For multiple target SRS, 4-arc VMAT produced clinically equivalent conformity, dose fall-off, 12 Gy isodose volume, and low isodose spill, and reduced treatment time compared to GK. Due to its similar plan quality and increased delivery efficiency, single-isocenter VMAT radiosurgery may constitute an attractive alternative to multi-isocenter radiosurgery for some patients.

Copyright (C) by the Congress of Neurological Surgeons

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