Dose comparison of robustly optimized intensity modulated proton therapy (IMPT) vs IMRT and VMAT photon plans for testicular seminoma

Figures & data

Table 1. Patient and treatment characteristics.

Patient	Age (at treatment)	GTV volume (cm3)	Boost position	Dose (Gy) (primary + boost)	Clinical Photon Technique
1	46	2.2	Pre-Caval	24 + 10	3 field IMRT
2	39	8.9	Paraaortic L	24 + 10	3 field IMRT
3	45	12.7	Paraaortic L	20 + 10	4 field IMRT
4	33	2.2	Pre-Caval	20 + 10	4 field IMRT
5	37	2.6	Ilaca Int R	25 + 10	2 arc VMAT
6	28	2.9	Paraaortic L	25 + 10	2 arc VMAT
7	30	5.7	Pre-Caval	25 + 10	2 arc VMAT
8	54	8.4	Paraortic L	20 + 10	2 arc VMAT
9	62	8.1	Paraaortic L	25 + 10	2 arc VMAT
10	58	5.5	Paraortic L	25 + 10	2 arc VMAT

GTV: Gross Tumour Volume; CTV: Clinical Target Volume; E: Elective; T: Metastatic lymph node(s) boost; L: Left; R: Right; INT: Internal.

Figure 1. Box plots for mean doses for body outline, bowel bag, bladder, spinal cord, duodenum, kidney left, kidney right, pancreas and stomach. IMPT (red), IMRT (blue), VMAT (green). Box plots define the interquartile range (IQR) with the 25th and 75th percentile as top and bottom. The whisker length is defined as 1.5 times the IQR and outliers beyond are marked (Black).

Figure 2. Dose distribution for CTV-E shown for IMRT, VMAT and IMPT. Top row: Transversal view; Middle row: Sagittal view; Bottom row: Coronal view. Shown is the 50% dose colour wash.

Table 2. Results - Median (range) D_mean and median (range) relative EAR.

OAR	IMPT (Mean, Gy)	IMRT (Mean, Gy)	VMAT (Mean, Gy)	p (IMPT vs IMRT)	p (IMPT vs VMAT)	Rel. EAR (IMPT vs IMRT)	Rel. EAR (IMPT vs VMAT)	p (IMPT vs IMRT)	p (IMPT vs VMAT)
Body Outline	2.9	4.5	5.8	0.002*	0.002*	0.59	0.33	0.002*	0.002*
	(1.5–3.3)	(3.2–6.5)	(3.8–12.5)			(0.45–0.69)	(0.28–0.36)
Bladder	2.0	4.2	7.4	0.002*	0.002*	0.36	0.30	0.002*	0.002*
	(0–5.4)	(1.0–8.5)	(2.2–14.5)			(0.05–0.69)	(0.03–0.78)
Duodenum	17.0	20.6	22.2	0.010*	0.002*	1.08	1.50	0.375	0.002*
	(11.4–25.4)	(13.4–29.0)	(16.0–29.6)			(0.55–1.57)	(1.56–1.81)
Pancreas	10.6	16.2	14.7	0.002*	0.004*	0.78	1.17	0.492	0.160
	(3.3–19.7)	(6.5–24.5)	(7.7–21.3)			(0.51–1.40)	(0.72–1.94)
Stomach	1.2	8.7	6.0	0.002*	0.002*	0.23	0.18	0.002*	0.002*
	(0–3.6)	(2.8–14.8)	(2.0–11.3)			(0.01–0.54)	(0.01–0.47)
Bowel Bag (small intestine)	4.4	11.6	11.9	0.002*	0.002*	0.37	0.72	0.002*	0.020*
	(2.4–6.3)	(8.0–13.9)	(9.5–15.8)			(0.27–0.44)	(0.35–1.07)
Bowel Bag (Colon)						0.40	0.36	0.002*	0.002*
						(0.29–0.53)	(0.25–0.40)
Spinal Cord	15.1	23.6	13.3	0.002*	0.084	0.71	1.03	0.002*	0.160
	(9.9–18.7)	(19.6–26.8)	(7.2–16.7)			(0.58–0.84)	(0.86–1.66)
Kidney L	3.5	4.3	7.0	0.160	0.002*
	(1.4–6.8)	(2.2–9.4)	(3.8–12.5)
Kidney R	3.5	4.5	7.0	0.065	0.002*
	(1.0–5.8)	(1.1–8.7)	(4.8–14.3)

Rel.: Relative.

EAR: excess absolute risk per 10.000 (according to Schenider et al. [17]).

*p < .05 after Holm-Bonferroni correction.

Figure 3. Top row: The excess absolute risk (EAR) per 10.000 persons per year of secondary cancer for IMPT (Red), IMRT (blue) and VMAT (green), respectively, according to Schneider et al. [17]. Bottom row: The relative EAR for IMPT vs IMRT (blue) and IMPT vs VMAT (green). Bladder, duodenum, pancreas, stomach, spinal cord, bowel bag (small intestine), bowel bag (colon), and body outline. Box plots define the interquartile range (IQR) with the 25th and 75th percentile as top and bottom. The whisker length is defined as 1.5 times the IQR and outliers beyond are marked (Black).

Jabbour SK, Hashem SA, Bosch W, et al. Upper abdominal normal organ contouring guidelines and atlas: a radiation therapy oncology group consensus. Pract Radiat Oncol. 2014;4(2):82–89. doi: 10.1016/j.prro.2013.06.004.

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Data availability statement

Due to the national legislation it is not possible to share data.