Non–coplanar whole brain radiotherapy is an effective modality for parotid sparing

BACKGROUND: The purpose of this study was to evaluate the efficacy and feasibility of non–coplanar whole brain radiotherapy (NC–WBRT) for parotid sparing. METHODS: Fifteen cases, previously treated with WBRT were selected. NC–WBRT plans were generated. The beam arrangement for the non–coplanar plans consisted of superior anterior, right, and left beams. After generation of the non–coplanar plans a field–in–field technique was applied to the bilateral parallel opposed beams in order to reduce maximum dose and increase dose homogeneity. The NC–WBRT plans were subsequently compared with the previously generated bilateral WBRT (B–WBRT) plans. A field–in–field technique was also used with the B–WBRT plans according to our departmental protocol. As per our institutional practice a total dose of 30 Gy in 10 fractions of WBRT was administered 5 days a week. RESULTS: The mean dose to the parotid gland for the two different plans were 16.2 Gy with B–WBRT and 13.7 Gy with NC–WBRT (p<0.05). In the NC–WBRT plan, the V(5Gy), V(10Gy), V(15Gy), V(20Gy), and V(25Gy) of the parotid were significantly lower (p<0.05) than those of the B–WBRT plan. The D(max) of the lens was also lower by 10% with NC–WBRT. CONCLUSION: The use of NC–WBRT plans could be a simple and effective method to reduce irradiated volumes and improve the dose–volume parameters of the parotid gland.