A planning comparison of dose patterns in organs at risk and predicted risk for radiation induced malignancy in the contralateral breast following radiation therapy of primary breast using conventional, IMRT and Volumetric modulated arc treatment techniques

Figures & data

Table I.  Summary of DVH analysis for PTV and OAR for the cohort of 8 breast cancer patients included in this study, for 4 fields conventional, IMRT and RA treatment techniques. Data are shown as mean values plus or minus one standard deviation; in brackets the range. The patients were treated planned for 6 MV beams to a dose of 50 Gy in 25 fractions.

	Conv. Plans	IMRT Plans	RA Plans
	Mean±Std dev. [range]
Target
Mean(Gy)	50.0±0.0 [50, 50]	50.0±0.0 [50, 50]	50.0±0.0 [50, 50]
Min(Gy)	39.3±8.7 [20.8, 45.5]*	31.3±2.6 [27.2, 35.3]	39.2±1.1 [37.5, 40.7]
Max(Gy)	56.5±1.0 [55.5, 58.7]*	59.9±1.7 [58.7, 64.0]	54.8±0.8 [53.4, 55.8] *
V90%	97.1±2.5 [93.1, 99.6]	96.3±1.5 [93.8, 98.4]	98.5±0.7 [97.1, 99.4]
CI90%	2.0±0.2 [1.7, 2.4]	1.2±0.2 [1.0, 1.7] *	1.3±0.00 [1.2, 1.3]*
Std.d.	2.7±0.9 [1.8, 4.5]	3.4±2.2 [2.1, 8.7]	1.76±0.24 [1.39, 2.099]*
D1%	54.3±1.0 [52.3, 55.8]*	56.2±0.7 [55.5, 57.6]	53.3±0.5 [52.7, 53.9] *
D2%	54.0±1.0 [51.8, 55.3]*	55.5±0.4 [55.1, 56.2]	53.0±0.4 [52.4, 53.4] *
D98%	45.9±3.6 [39.8, 52.7]	43.8±1.0 [42.3, 45.5]	45.5±0.7 [44.6, 46.6]
D99%	42.7±4.3 [34.7, 46.2]	42.5±1.2 [40.7, 44.2]	44.8±0.7 [43.9, 46.1]
Heart
mean dose	2.6±1.6 [1.0, 4.8] *	5.5±1.3 [4.1, 7.3]	4.6±2.4 [2.4, 8.6]
max(Gy)	23.2±21.2 [3.9, 47.2]	20.4±11.8 [10.6, 43.9]	14.4±10.9 [6.8, 34.5]
V4-Gy	8.9±10.3 [0.1, 25.6] *	63.8±20.1 [42.3, 90.1]	41.1±30.4 [6.3, 75.5]
D1%	20.2±19.0 [2.8, 43.8]	13.4±4.0 [9.4, 19.0]	11.6±8.8 [4.9, 28.2]
D2%	17.6±17.1 [2.4, 42.1]	12.2±3.4 [9.0, 16.2]	10.6±7.8 [4.6, 25.5]
IPSI lung
Mean dose	18.0±1.0 [17.2, 20.3]	13.6±1.8 [11.6, 16.5]*	14.3±0.9 [13.2, 15.6] *
max(Gy)	52.3±1.9 [49.8, 55.4]	53.1±1.5 [51.0, 55.6]	46.9±1.3 [45.3, 48.9] *
V10-Gy	52.4±2.8 [48.7, 56.6]	54.5±11.8 [41.8, 77.2]	55.2±5.3 [46.4, 62.4]*
V20-Gy	41.5±2.7 [38.0, 46.7]	18.6±3.8 [14.5, 24.9] *	24.0±3.3 [19.8, 29.8] *
D1%	48.2±0.9 [46.8, 49.4]	43.5±2.5 [40.9, 48.5] *	41.8±1.4 [39.1, 43.4] *
D2%	47.5±0.8 [46.2, 48.6]	40.9±2.8 [37.8, 46.6] *	40.1±1.4 [37.5, 41.4] *
Cont. Lung
Mean dose*	1.4±0.3 [1.0, 2.0]*	2.9±0.4 [2.2, 3.5]	2.9±0.4 [2.5, 3.8]
max(Gy)	28.7±17.2 [10.5, 53.3]	15.5±8.2 [0.3, 27.2]	8.3±2.3 [6.3, 10.7] *
V10-Gy	1.2±1.7 [0.0, 4.8]	1.3±1.1 [0.1, 3.1]	0.2±0.4 [0.0, 1.1]
V20-Gy	0.1±0.1 [0.0, 0.2]	0.0±0.0 [0.0, 0.0]	0.0±0.0 [0.0, 0.0]
D1%	12.3±14.8 [3.4, 47.7]	10.0±1.8 [7.5, 12.3]	6.8±1.9 [5.1, 10.1]
D2%	11.1±15.2 [2.9, 47.0]	8.9±1.6 [6.7, 10.7]	6.4±1.7 [4.9, 9.4]
CB
mean dose	2.2±1.0 [1.3, 4.2]	2.9±0.8 [1.6, 4.2]	2.0±0.4 [1.6, 2.6]
max(Gy)	19.3±9.3 [15.2, 42.1]	15.6±6.9 [6.4, 29.3]	6.4±0.8 [4.9, 7.6] *
V10-Gy	7.1±5.2 [1.5, 17.0]	0.7±0.8 [0.0, 2.3] *	0.0±0.0 [0.0, 0.0] *
D1%	13.8±2.4 [11.5, 19.0]	9.1±2.9 [3.9, 14.2] *	4.3±0.7 [3.2, 5.4] *
D2%	12.3±2.2 [8.2, 15.3]	7.9±2.1 [3.7., 10.6] *	3.9±0.6 [3.0, 4.8] *

* Value significantly different from the other techniques with p < 0.05

Figure 1.  Dose volume histograms in cumulative form showing the dose distribution for CB and target using conventional treatment technique (upper panel), IMRT (middle panel) and RapidArc (lower panel).

Table II.  Mean dose to CB and ERR calculated using the linear and non-linear models for the 8 patients using standard conventional treatment technique, IMRT and volumetric modulated arc techniques. The mean CB dose is used to predict the risk for radiation induced malignancy in CB using the linear model. Calculations applying the non-linear model are based on the patients’ individual dose volume histogram and assuming α₁=0.002Gy⁻¹, α₂=0.25Gy⁻¹ and both α₁/β₁=α₂/β₂=4Gy.

Pat. No.	Mean CB dose conventional	ERR-linear conventional	ERR-nonlinear conventional
1	2.97	1.28	0.33
2	1.6	0.69	0.3
3	2.06	0.89	0.31
4	4.27	1.84	0.39
5	2.79	1.2	0.35
6	1.25	0.54	0.27
7	1.38	0.59	0.29
8	1.3	0.56	0.26
Mean	2.2±1.0	0.94±0.46	0.31±0.04
	IMRT	IMRT	IMRT
1	4.2	1.81	0.41
2	1.6	0.69	0.3
3	3.1	1.33	0.41
4	3.2	1.38	0.43
5	1.9	0.82	0.35
6	3	1.29	0.42
7	3	1.29	0.41
8	2.8	1.2	0.4
Mean	2.85±0.80	1.23±0.35	0.39±0.04
	RA	RA	RA
1	2.55	1.1	0.37
2	2.46	1.06	0.37
3	1.68	0.72	0.29
4	2.07	0.89	0.34
5	1.79	0.77	0.31
6	1.6	0.69	0.29
7	1.85	0.79	0.32
8	1.73	0.74	0.31
Mean	1.97±0.36	0.85±0.16	0.33±0.03

Figure 2.  ERR predicted by linear and non linear models for radiation induced malignancy in CB for three different techniques in 8 included patients is shown in upper and lower panels, respectively.