Feasibility study on protection of key organs in the whole brain radiotherapy with simultaneous integrated boost in patients with 1-3 brain metastases

To explore the feasibility of three radiotherapy techniques to realize simultaneous modulated accelerated radiation therapy for elective brain (SMART-Brain) in patients with 1-3 brain metastases.

Intensity modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT) and helical tomotherapy (HT) were utilized to design radiotherapy plans for 20 patients with 1-3 brain metastases from lung cancer who underwent SMART-Brain, and the dosimetry parameters of the target volume and organs at risk (OARs) were compared.

For planning gross tumor volume (PGTV), D98% (near minimum) and conformity index (CI) of VMAT plan were significantly better than IMRT plan. For the planning target volume 1 (PTV1), HT plan provided better D98%, D2% (near maximum dose), V30Gy (target volume percent of 30Gy dose covering) and CI. In terms of the expose dose of hippocampus, HT plan had advantages in Dmean (mean dose), and its Dmax (maximum dose) was equivalent to VMAT plan, which was better than IMRT plan. HT and VMAT plans had a lower Dmax of optic chiasm, and VMAT plan was better in terms of dose limitation of scalp. In terms of lens protection, IMRT and VMAT plans were better than HT plan. There was no statistical difference in other dosimetry parameters.

For most patients, all three radiotherapy techniques met clinical requirements. VMAT and HT plans were superior to IMRT plan. It was recommended that VMAT or HT radiotherapy techniques should be selected to implement SMART-Brain according to the local reality of the radiotherapy facilities.