Dosimetric comparison of postoperative whole pelvic radiotherapy for endometrial cancer using three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and helical tomotherapy

Figures & data

Table I. Dose-volume constraints used in IMRT

Structures	Constraints
PTV	Minimal dose, 47.5 Gy; maximal dose 55 Gy; ·95% of PTV receiving 50 Gy
Bowel	·35% of bowel receiving ·35 Gy
Bladder	·40% of bladder receiving ·40 Gy
Rectum	·60% of bladder receiving ·40 Gy

Abbreviations: IMRT = intensity-modulated radiotherapy; PTV = planning target volume.

Table II. Summary of PTV coverage data for 3D-CRT, IMRT and HT plans

Plans	Items	PTV95 (%)	PTV100 (%)	PTV105 (%)	PTV110 (%)	CI	HI
3D-CRT	Mean	100.00	95.30	63.80	1.10	0.61	1.08
IMRT	Mean	100.00	95.60	48.80	7.60	0.87	1.10
	·	0.00	0.30	−15.10	6.50	0.27	0.02
	p	0.48	0.52	0.08	0.01	0.00	0.01
HT	Mean	99.80	95.80	15.60	0.60	0.87	1.07
	·	−0.20	0.50	−48.27	−0.50	0.26	−0.01
	p	0.35	0.29	0.00	0.33	0.00	0.01

Abbreviations: 3D-CRT = three dimensional conformal radiotherapy; HT = helical tomotherapy; · = change; PTV₉₅, PTV₁₀₀, PTV₁₀₅, PTV₁₁₀ = percentage of PTV receiving 95%, 100%, 105%, 110% of prescription dose, respectively; D_mean = mean dose; ID = integral dose; CI = conformity index; HI = homogeneity index; other abbreviations as in Table I.

Figure 1. Typical axial dose distributions obtained with three-dimensional conformal radiotherapy, intensity-modulated radiotherapy, and helical tomotherapy. The shown isodose lines included 53.5 Gy, 50.0 Gy, 47.5 Gy, 45.0 Gy, 20.0 Gy and 10.0 Gy. The PTV was shown in blue.

Table III. Summary of OARs and normal tissue dose distribution for 3D-CRT, IMRT and HT plans

Structures		Items	V5	V10	V20	V30	V40	V50	Dmean (Gy)
Bowel	3D-CRT	Mean	0.91	0.81	0.70	0.45	0.26	0.17	28.15
	IMRT	Mean	0.93	0.85	0.63	0.38	0.20	0.09	25.99
		P	0.08	0.07	0.00	0.01	0.01	0.00	0.01
	HT	Mean	0.98	0.91	0.64	0.33	0.19	0.08	26.28
		P	0.00	0.00	0.00	0.00	0.01	0.00	0.01
Rectum	3D-CRT	Mean	0.99	0.98	0.97	0.94	0.88	0.69	48.32
	IMRT	Mean	0.99	0.98	0.97	0.93	0.64	0.27	42.57
		P	0.53	0.17	0.77	0.61	0.00	0.00	0.00
	HT	Mean	1.00	1.00	0.98	0.85	0.57	0.25	41.28
		P	0.18	0.08	0.16	0.01	0.00	0.00	0.00
Bladder	3D-CRT	Mean	1.00	1.00	0.99	0.97	0.68	0.50	45.09
	IMRT	Mean	1.00	0.99	0.89	0.68	0.38	0.17	35.81
		P	0.68	0.57	0.07	0.00	0.00	0.00	0.00
	HT	Mean	1.00	1.00	0.86	0.51	0.29	0.14	32.79
		P	–	0.68	0.02	0.00	0.00	0.00	0.00
Pelvic bone marrow	3D-CRT	Mean	0.95	0.88	0.80	0.48	0.27	0.15	30.39
	IMRT	Mean	0.92	0.84	0.65	0.45	0.24	0.09	27.29
		P	0.00	0.00	0.00	0.03	0.01	0.00	0.00
	HT	Mean	0.97	0.91	0.69	0.44	0.24	0.09	28.40
		P	0.00	0.00	0.00	0.01	0.00	0.00	0.00
Normal tissue	3D-CRT	Mean	0.71	0.59	0.49	0.23	0.09	0.04	19.70
	IMRT	Mean	0.79	0.63	0.37	0.18	0.07	0.01	18.09
		P	0.00	0.03	0.00	0.00	0.00	0.00	0.00
	HT	Mean	0.92	0.81	0.42	0.17	0.06	0.01	20.56
		P	0.00	0.00	0.00	0.00	0.00	0.00	0.06

The correlation and t cannot be computed because the standard error of the difference is 0.

Abbreviations: OARs = organs at risk; V₅, V₁₀, V₂₀, V₃₀, V₄₀, V₅₀ = percentage of organs at risk receiving 5 Gy, 10 Gy, 20 Gy, 30 Gy, 40 Gy and 50 Gy, respectively; other abbreviations as in Table II.

Table IV. Integral dose to OARs and normal tissue for 3D-CRT, IMRT and HT plans

		IMRT			HT
Structures	3D-CRT Mean (Gy-L)	Mean (Gy-L)	%·	p	Mean (Gy-L)	%·	p
Bowel	24.20	22.40	−7.39	0.00	22.67	−6.32	0.01
Rectum	4.20	3.70	−12.62	0.00	3.60	−14.29	0.00
Bladder	15.86	11.87	−25.16	0.01	11.37	−28.37	0.01
Pelvic bone marrow	40.00	36.00	−10.25	0.00	37.65	−5.88	0.00
Normal tissue	245.00	225.50	−7.96	0.00	256.85	4.83	0.04

Abbreviations: %· = percentage of change; other abbreviations as in Table II and III.