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Feasibility of extreme dose escalation for glioblastoma multiforme using 4π radiotherapy.

Nguyen D, Rwigema JC, Yu VY, Kaprealian T, Kupelian P, Selch M, Lee P, Low DA, Sheng K - Radiat Oncol (2014)

Bottom Line: The 4π plans resulted in superior dose gradient indices, as indicated by >20% reduction in the R50, compared to the clinical plans.Among all of the 4π cases, when compared to the clinical plans, the maximum and mean doses were significantly reduced (p < 0.05) by a range of 47.01-98.82% and 51.87-99.47%, respectively, or unchanged (p > 0.05) for all of the non-brain OARs.Dose escalation to 100 Gy to the GTV or additional margin expansion while meeting clinical critical organ dose constraints is feasible. 100 Gy to the PTV result in higher normal brain doses but may be tolerated when delivered in proportionally increased treatment fractions.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza Way, Suite B265, Los Angeles, USA. dannguyen@mednet.ucla.edu.

ABSTRACT

Background: Glioblastoma multiforme (GBM) frequently recurs at the same location after radiotherapy. Further dose escalation using conventional methods is limited by normal tissue tolerance. 4π non-coplanar radiotherapy has recently emerged as a new potential method to deliver highly conformal radiation dose using the C-arm linacs. We aim to study the feasibility of very substantial GBM dose escalation while maintaining normal tissue tolerance using 4π.

Methods: 11 GBM patients previously treated with volumetric modulated arc therapy (VMAT/RapidArc) on the NovalisTx™ platform to a prescription dose of either 59.4 Gy or 60 Gy were included. All patients were replanned with 30 non-coplanar beams using a 4π radiotherapy platform, which inverse optimizes both beam angles and fluence maps. Four different prescriptions were used including original prescription dose and PTV (4πPTVPD), 100 Gy to the PTV and GTV (4πPTV100Gy), 100 Gy to the GTV only while maintaining prescription dose to the rest of the PTV (4πGTV100Gy), and a 5 mm margin expansion plan (4πPTVPD+5mm). OARs included in the study are the normal brain (brain - PTV), brainstem, chiasm, spinal cord, eyes, lenses, optical nerves, and cochleae.

Results: The 4π plans resulted in superior dose gradient indices, as indicated by >20% reduction in the R50, compared to the clinical plans. Among all of the 4π cases, when compared to the clinical plans, the maximum and mean doses were significantly reduced (p < 0.05) by a range of 47.01-98.82% and 51.87-99.47%, respectively, or unchanged (p > 0.05) for all of the non-brain OARs. Both the 4πPTVPD and 4π GTV100GYplans reduced the mean normal brain mean doses.

Conclusions: 4π non-coplanar radiotherapy substantially increases the dose gradient outside of the PTV and better spares critical organs. Dose escalation to 100 Gy to the GTV or additional margin expansion while meeting clinical critical organ dose constraints is feasible. 100 Gy to the PTV result in higher normal brain doses but may be tolerated when delivered in proportionally increased treatment fractions. Therefore, 4π non-coplanar radiotherapy on C-arm gantry may provide an accessible tool to improve the outcome of GBM radiotherapy through extreme dose escalation.

No MeSH data available.


Related in: MedlinePlus

Individual patient dosimetry comparisons between clinical VMAT plans and the various 4π plans.
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Fig2: Individual patient dosimetry comparisons between clinical VMAT plans and the various 4π plans.

Mentions: Figure 2 compares the normal brain maximum dose, mean dose, V30, and V36 between the clinical plan and the 4π plans. The 4πPTVPD plans significantly reduced (p < 0.001) the mean brain dose from 21.94 Gy to 16.56 Gy and slightly increased the maximum normal brain doses (p < 0.001) from 63.24 to 64.88 Gy. The maximum normal brain doses increased (p < 0.001) in the 4πPTV100Gy and 4πGTV100Gy plans to 108.71 Gy and 98.51 Gy respectively. The 4πPTV100Gy plans also significantly increased (p < 0.001) the mean brain dose to 27.60 Gy (26%), while the 4πGTV100Gy significantly decreased (p < 0.001) the mean brain dose to 17.61 Gy (20%). For the 4πPTVPD+5mm plans, the maximum brain dose slightly increased (p < 0.001) from 63.24 Gy to 64.94 Gy, and the brain mean dose was statistically unchanged (p > 0.05).Figure 2


Feasibility of extreme dose escalation for glioblastoma multiforme using 4π radiotherapy.

Nguyen D, Rwigema JC, Yu VY, Kaprealian T, Kupelian P, Selch M, Lee P, Low DA, Sheng K - Radiat Oncol (2014)

Individual patient dosimetry comparisons between clinical VMAT plans and the various 4π plans.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4230756&req=5

Fig2: Individual patient dosimetry comparisons between clinical VMAT plans and the various 4π plans.
Mentions: Figure 2 compares the normal brain maximum dose, mean dose, V30, and V36 between the clinical plan and the 4π plans. The 4πPTVPD plans significantly reduced (p < 0.001) the mean brain dose from 21.94 Gy to 16.56 Gy and slightly increased the maximum normal brain doses (p < 0.001) from 63.24 to 64.88 Gy. The maximum normal brain doses increased (p < 0.001) in the 4πPTV100Gy and 4πGTV100Gy plans to 108.71 Gy and 98.51 Gy respectively. The 4πPTV100Gy plans also significantly increased (p < 0.001) the mean brain dose to 27.60 Gy (26%), while the 4πGTV100Gy significantly decreased (p < 0.001) the mean brain dose to 17.61 Gy (20%). For the 4πPTVPD+5mm plans, the maximum brain dose slightly increased (p < 0.001) from 63.24 Gy to 64.94 Gy, and the brain mean dose was statistically unchanged (p > 0.05).Figure 2

Bottom Line: The 4π plans resulted in superior dose gradient indices, as indicated by >20% reduction in the R50, compared to the clinical plans.Among all of the 4π cases, when compared to the clinical plans, the maximum and mean doses were significantly reduced (p < 0.05) by a range of 47.01-98.82% and 51.87-99.47%, respectively, or unchanged (p > 0.05) for all of the non-brain OARs.Dose escalation to 100 Gy to the GTV or additional margin expansion while meeting clinical critical organ dose constraints is feasible. 100 Gy to the PTV result in higher normal brain doses but may be tolerated when delivered in proportionally increased treatment fractions.

View Article: PubMed Central - PubMed

Affiliation: Department of Radiation Oncology, University of California, Los Angeles, 200 Medical Plaza Way, Suite B265, Los Angeles, USA. dannguyen@mednet.ucla.edu.

ABSTRACT

Background: Glioblastoma multiforme (GBM) frequently recurs at the same location after radiotherapy. Further dose escalation using conventional methods is limited by normal tissue tolerance. 4π non-coplanar radiotherapy has recently emerged as a new potential method to deliver highly conformal radiation dose using the C-arm linacs. We aim to study the feasibility of very substantial GBM dose escalation while maintaining normal tissue tolerance using 4π.

Methods: 11 GBM patients previously treated with volumetric modulated arc therapy (VMAT/RapidArc) on the NovalisTx™ platform to a prescription dose of either 59.4 Gy or 60 Gy were included. All patients were replanned with 30 non-coplanar beams using a 4π radiotherapy platform, which inverse optimizes both beam angles and fluence maps. Four different prescriptions were used including original prescription dose and PTV (4πPTVPD), 100 Gy to the PTV and GTV (4πPTV100Gy), 100 Gy to the GTV only while maintaining prescription dose to the rest of the PTV (4πGTV100Gy), and a 5 mm margin expansion plan (4πPTVPD+5mm). OARs included in the study are the normal brain (brain - PTV), brainstem, chiasm, spinal cord, eyes, lenses, optical nerves, and cochleae.

Results: The 4π plans resulted in superior dose gradient indices, as indicated by >20% reduction in the R50, compared to the clinical plans. Among all of the 4π cases, when compared to the clinical plans, the maximum and mean doses were significantly reduced (p < 0.05) by a range of 47.01-98.82% and 51.87-99.47%, respectively, or unchanged (p > 0.05) for all of the non-brain OARs. Both the 4πPTVPD and 4π GTV100GYplans reduced the mean normal brain mean doses.

Conclusions: 4π non-coplanar radiotherapy substantially increases the dose gradient outside of the PTV and better spares critical organs. Dose escalation to 100 Gy to the GTV or additional margin expansion while meeting clinical critical organ dose constraints is feasible. 100 Gy to the PTV result in higher normal brain doses but may be tolerated when delivered in proportionally increased treatment fractions. Therefore, 4π non-coplanar radiotherapy on C-arm gantry may provide an accessible tool to improve the outcome of GBM radiotherapy through extreme dose escalation.

No MeSH data available.


Related in: MedlinePlus