Daily dosimetric variation between image-guided volumetric modulated arc radiotherapy and MR-guided daily adaptive radiotherapy for prostate cancer stereotactic body radiotherapy

Figures & data

Table 1. Patients characteristics (n = 40).

Median age years (range)	69 (57–80)
Risk class:
Low	24 (60%)
Intermediate	16 (40%)
Treatment group:
Daily adaptive MR-guided (group 1)	10 (25%)
CBCT without fiducial (group 2)	20 (50%)
CBCT with fiducial (group 3)	10 (25%)

MR: magnetic resonance; CBCT: cone-beam CT.

Figure 1. Boxplot of the average rectum volume divided according to treatment group, and planning and treatment imaging.

Figure 2. Incidence of constraints violation among treatment groups.

Table 2. Target and organ at risk volume.

	Group 1 (n = 10)	Group 2 (n = 20)	Group 3 (n = 10)
Mean CTV volume at simulation (cc)	50.79 (29.7–77.8)	55.65 (35.4–77.2)	58.03 (43.7–73.8)
Mean CTV volume during treatment (cc)	54.68 (23.6–86.6)	56.61 (32–81.2)	57.93 (37.7–85.1)
Mean rectum volume at simulation (cc)	50.36 (34.2–68.3)	75.47 (46.1–131.2)	88.25 (58.3–131.2)
Mean rectum volume during treatment (cc)	50.49 (34–70.3)	77.53 (29.4–155.9)	86.7 (38.1–219.8)
Mean bladder volume at simulation (cc)	261.26 (114.6–464.5)	275.88 (126.5–437.5)	311.73 (108.4–840.5)
Mean bladder volume during treatment (cc)	252.86 (112–481.7)	281.67 (132.8–587.5)	291.93 (114.6–661.9)

CTV: clinical target volume.

Table 3. DVH parameters.

Average (range)	Criterion
	Simulation MR	Treatment MR	Simulation CT without fiducials	CBCT without fiducials	Simulation CT with fiducials	CBCT with fiducials
CTV 95/98	96.84% (95.08–98.9)	98.09% (97.2–99)	95.25% (71.1–100)	96.79% (69.8–100)	95.74% (87.5–99.9)	98.8% (97.63–100)
rectumV18Gy ≤35%	19.98% (17.86–24.48)	20.61% (16.21–27.17)	20.48% (8.2–35)	20.79% (1.46–52)	16.21% (3.4–29.9)	20.4% (6.65–48.4)
rectumV28Gy ≤10%	7.88% (6.62–9.24)	8.04% (4.62–10.99)	9.08% (1.6–15.5)	9.19% (0–33.6)	6.31% (0.68–10.1)	9.33% (1.96–24.1)
rectumV32Gy ≤5%	3.29% (2.04–4.91)	3.42% (0.88–7.82)	4.67% (0.4–9.8)	5.67% (0–27)	3.13% (0–5)	5.73% (0.74–14.2)
rectumV35Gy ≤ 1%	0.07% (0–0.43)	0.09% (0–0.55)	2.26% (0–3)	2.32% (0–16.6)	0.31% (0–1)	2.53% (0–8.72)
rectumDmax 1cc 37.45Gy	35.55 Gy (34.6–36.7)	35.45 Gy (34.3–37.7)	35.79Gy (34.5–36.7)	36.61Gy (28.36–38.9)	35.77Gy (33.8–36.9)	37.6Gy (35.33–40.2)
bladderV35Gy ≤1%	0.24% (0–0.59)	0.25% (0–1)	0.56% (0–4.6)	1.53% (0–7.7)	0.36% (0–0.99)	1.3% (0.1–3.8)
bladderDmax 1cc 37.45Gy	35.63Gy (34.9–36.5)	35.48Gy (34.6–36.4)	37.34Gy (35.5–37.6)	37.27Gy (31.7–39.4)	37.5Gy (35.64–37.4)	37.7Gy (63.2–39.36)

MR: magnetic resonance; CBCT: cone-beam CT.