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

The purpose of this study was to evaluate the efficacy and feasibility of non-coplanar whole brain radiotherapy (NC-WBRT) for parotid sparing.

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.

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.

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.