A dosimetric comparison of ultra-hypofractionated passively scattered proton radiotherapy and stereotactic body radiotherapy (SBRT) in the definitive treatment of localized prostate cancer

Figures & data

Table I. Selected comparative dose-volume indices.

OAR/target	Dosimetric index	Cyberknife	Proton	p-Value
PTV	V90%	99.8%	99.99%	0.002
	V100%	95.9%	95%	0.006
	V105%	78.99%	21.57%	0.002
	Mean dose (Gy/CGE)	39.6	37.6	0.002
Prostatic urethra	V100%	98.96%	99.93%	0.125
	V105%	14.85%	30.72%	0.11
	Mean dose (Gy/CGE)	37.6	37.9	0.014
Rectum	V25%	38.88%	21.13%	0.002
	V50%	18.83%	13.49%	0.006
	V75%	8.54%	7.99%	0.77
	V90%	3.63%	4.37%	0.23
	V100%	0.79%	1.09%	0.22
	V105%	0.14%	0%	0.031
	Mean dose (Gy/CGE)	10.6	6.66	0.002
Bladder	V25%	73.02%	49.32%	0.004
	V50%	29.66%	37.4%	0.037
	V75%	13.44%	25.33%	0.004
	V90%	7.14%	15.86%	0.004
	V100%	3.0%	5.82%	0.037
	V105%	0.96%	0.02%	0.002
	Mean dose (Gy/CGE)	15.4	13.7	0.56
Penile bulb	V25%	55.33%	22.72%	0.002
	V50%	20.19%	8.61%	0.004
	V75%	3.66%	0.69%	0.031
	Mean dose (Gy/CGE)	11.4	5.19	0.002
Membranous urethra	V75%	92.61%	86.99%	0.078
	V90%	75.93%	64.13%	0.027
	V100%	45.91%	21.0%	0.004
	V105%	9.23%	0.13%	0.004
	Mean dose (Gy/CGE)	34.4	32.2	0.006
Right femoral head	V10%	43.5%	86.92%	0.002
	V25%	3.79%	80.69%	0.002
	Mean dose (Gy/CGE)	7.12	10.4	0.002
Left femoral head	V10%	82.81%	82.31%	0.77
	V25%	28.27%	76.32%	0.002
	Mean dose (Gy/CGE)	4.0	10.9	0.002

Figure 1. (A) Treatment planning axial, sagittal, and coronal CT images of a representative patient with corresponding prostate, rectum, bladder, penile bulb, membranous urethra, and prostatic urethra contours. Isodose lines for the 100% (blue), 50% (purple), and 10% (yellow) prescription dose for the Cyberknife (CK) (left panel) and proton (right panel) treatment plans are shown. (B) Patient-averaged dose-volume histograms of the planning target volume and box plots of the conformality index of CK (blue) and proton (red) treatment plans.

Figure 2. Patient-averaged dose-volume histograms of the organs at risk.