Hippocampal avoidance with volumetric modulated arc therapy in whole brain irradiation – the first experience at vinmec hospital
Abstract
Volumetric modulated arc therapy (VMAT) can provide appropriate dose distribution to Whole Brain (WBRT) with Hippocampus Avoidance (HA) and Simultaneous Integrated Boost (SIB) to metastases with high dose as Stereotactic radiotherapy (SRT) for brain nodules.
Purpose: This study aimed at assessing the initial experience of using VMAT for brain metastases and hippocampal avoidance at the Radiotherapy Center - Vinmec Times City International Hospital.
Materials and Methods: 03 patients diagnosed with lung cancer (02), rectal cancer (01), good performance status and life expectancy of ≥ 3 months, who were indicated for palliative whole-brain radiotherapy. Delineation of brain and organs at risk including the hippocampus, optic nerve, optic chiasm, eye and brain stem had determined based on magnetic resonance imaging and simulation computed tomography. Radiotherapy is planned on the Eclipse - version 13.0 planning system (Varian, Palo Alto, CA, USA). WBRT and SIB were integrated into a single plan.
Results: Three patients with 09 brain metastasis were treated from July 2016 to June 2017 using the VMAT radiotherapy technique at the Radiotherapy Center - Vinmec International Hospital. Mean follow up time was 11.0 months. For 03 patients, BMs arose from primary lung cancer (n = 2) and for the remaining one patient from primary rectal cancer (n = 1). The median WBRT dose was 29 Gy with a median SIB dose for BMs of 57 Gy (3Gy/fraction. Mean values for BMs were as follows: GTV = 15.9cc, PTV = 67.2cc, conformity index = 1,3; homogeneity index = 0,12. The mean hippocampal dose is 9.9 Gy and mean VMAT treatment time from beam on to beam off for one fraction was 2.4 minutes for two rounds. All 09 lesions can be controlled at the time of analysis. Good tolerability treatment.
Conclusion: VMAT for BMs is feasible, safe and associated with similar survival times and toxicities to conventional SRT+/−WBRT. The advantage of VMAT is that WBRT and SRT can be delivered at the same time on one machine.