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Int J Radiat Oncol Biol Phys. 2019 Jul 5. pii: S0360-3016(19)33443-1. doi: 10.1016/j.ijrobp.2019.06.2543. [Epub ahead of print]

Single-Fraction Stereotactic Radiosurgery vs. Hippocampal-Avoidance Whole Brain Radiotherapy for Patients with 10-30 Brain Metastases: A Dosimetric Analysis.

Author information

1
Department of Radiation Oncology, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
2
Division of Neurosurgery, St Michaels Hospital, University of Toronto, Toronto, Ontario, Canada.
3
Division of Neurosurgery, Sunnybrook Health Sciences Center, University of Toronto, Toronto, Ontario, Canada.
4
Departments of Medical Physics, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada.
5
Departments of Medical Physics, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario, Canada. Electronic address: Mark.Ruschin@sunnybrook.ca.

Abstract

PURPOSE:

To compare normal tissue dosimetry between hippocampal-avoidance whole brain radiotherapy (HA-WBRT) vs. stereotactic radiosurgery (SRS) in patients with 10-30 brain metastases, and describe a novel SRS strategy termed Spatially Partitioned Adaptive RadiosurgEry (SPARE).

METHODS:

A retrospective review identified SRS treatment plans with >10 brain metastases located >5mm from the hippocampi. Our Gamma Knife Icon SPARE (GKI-Spr) technique treats multiple metastases with single-fraction SRS partitioned over consecutive days, while limiting the total treatment time to ≤60 minutes per day. Hippocampal and normal brain dosimetry were compared between GKI-Spr, single-fraction single-day GKI (GKI-Sfr) and 30Gy in 10 fractions HA-WBRT. Dose metrics were converted to equivalent dose in 2Gy fractions (EQD2).

RESULTS:

Ten cases were analyzed. Compared to HA-WBRT, GKI-Spr significantly reduced the median EQD2 hippocampal maximum point dose (Dmax), mean dose (Dmean) and dose to 40% of the hippocampi (D40%) by 86%, 93% and 93%, respectively, and similarly for GKI-Sfr by 81%, 92% and 91%, respectively. The normal brain median Dmean was reduced by 95% with GKI-Spr and 94% with GKI-Sfr. Compared with GKI-Sfr, GKI-Spr further reduced all normal brain and hippocampal dose metrics (p<=0.014).

CONCLUSION:

GKI yields superior hippocampal and normal brain dosimetry compared to HA-WBRT, and GKI-Spr results in further dosimetric advantages.

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