Fig. 1

Radiation therapy to a total dose of 60.0 Gy, distributed in 30 fractions, was performed over a period of 6 weeks. In the first 4 weeks, the treatment was prescribed to the 100% isodose curve to a total dose of 40.0 Gy distributed in 20 fractions using opposing anterior-posterior fields (a, b). An additional 20.0 Gy was distributed in 10 fractions using 10 beams in the subsequent 2 weeks (c, d). The curves represent 100% isodose (red), 95% isodose (yellow), 50% isodose (purple), and 30% isodose (blue) (a, c). Gross tumor volume, clinical target volume, and planning target volume are shown in red, pink, and yellow, respectively (b, d)