Abstract:

Objective To perform a dosimetry study of the RapidArc technique for whole-brain radiotherapy involving simultaneous integrated boost （SIB） to brain metastases （BM） using volumetric modulated arc therapy （VMAT）. Methods Ten patients diagnosed with brain metastases were randomly selected and two treatment plans were designed for each patient. The RA plan involved whole-brain VMAT （30 Gy） and SIB to BM （45 Gy） delivered in 10 fractions. The Sum plan involved whole-brain 3DCRT （30 Gy） and SIB with VMAT to BM（15 Gy） delivered in 5 fractions. Results were compared using dose-volume histogram analysis. Results Both plans met the clinical requirements.Target conformity was better for the RA plan （0.99±0.00） than for the Sum plan（0.77±0.05； P<0.001）. V35 and V40 to brain were significantly lower in the RA plan than in the Sum plan（ P<0.05）. Average monitor units were 12% smaller with the RA plan than with the Sum plan. Conclusions The RA plan was similar to the Sum plan or better in terms of target dose distribution，monitor units and irradiation of some organs at risk，especially the normal brain tissue beside the metastases. These results suggest that whole-brain radiotherapy with SIB to BM using VMAT is superior for treating brain metastases.

Key words: Volumetric modulated arc therapy, Brain metastases, Whole brain radiotherapy, Dosimetry