Dose evaluation and risk estimation for secondary cancer in contralateral breast and a study of correlation between thorax shape and dose to organs at risk following tangentially breast irradiation during deep inspiration breath-hold and free breathing

Figures & data

Figure 1. Four thorax shape parameters are defined; A = Tangential diameter, B = central diameter, C = Lung orthogonal diameter and D = breast orthogonal diameter.

Table I. Summary of cumulative DVH analysis for CB for the cohort of 16 breast cancer patients included in this study, for tangential fields with FB (conventional) and DIBH techniques. CB data are shown as V1Gy, V3Gy, V5Gy, mean, and maximum.

Pat. No.	V1Gy (%)	V3Gy (%)	V5Gy (%)	Mean (Gy)	Maximum (Gy)
CB-Doses for DIBH-pIans
1	7.1	0.0	0.0	0.3	4.7
2	9.9	0.1	0.0	0.4	6.3
3	1.8	0.0	0.0	0.2	2.2
4	3.8	0.0	0.0	0.2	3.9
5	51.5	5.5	1.2	1.3	10.3
6	1.2	0.0	0.0	0.2	1.9
7	4.3	0.0	0.0	0.2	3.0
8	1.4	0.0	0.0	0.8	9.4
9	3.2	0.0	0.0	0.3	2.1
10	3.4	0.0	0.0	0.2	2.7
11	13.4	1.4	0.5	0.5	18.8
12	1.6	0.0	0.0	0.1	3.2
13	0.7	0.0	0.0	0.1	2.0
14	2.8	0.1	0.0	0.2	6.6
15	1.7	0.0	0.0	0.1	3.6
16	1.7	0.0	0.0	0.2	1.8
Mean	6.84	0.45	0.11	0.33	5.16
Median	3.0	0.0	0.0	0.2	3.4
Std	12.4	1.4	0.3	0.3	4.5
CB-Doses for FB-pIans
1	11.1	0.3	0.0	0.5	6.8
2	6.7	1.6	1.1	0.4	17.0
3	8.3	0.2	0.0	0.4	4.4
4	1.5	0.0	0.0	0.1	2.2
5	15.2	0.0	0.0	0.6	4.1
6	1.4	0.0	0.0	0.1	1.9
7	4.6	0.5	0.2	0.2	13.3
8	1.1	0.0	0.0	0.1	2.3
9	2.7	0.0	0.0	0.2	2.1
10	3.0	0.0	0.0	0.2	2.5
11	15.5	4.2	3.0	1.0	12.2
12	1.7	0.0	0.0	0.1	2.8
13	0.9	0.0	0.0	0.1	2.3
14	3.3	0.1	0.0	0.2	6.6
15	1.8	0.0	0.0	0.1	3.8
16	2.3	0.0	0.0	0.2	2.1
Mean	5.07	0.44	0.27	0.28	5.40
Median	2.9	0.0	0.0	0.2	3.3
Std	4.9	1.1	0.8	0.2	4.7

Table II. Contour measurements data. Four parameters are made to define thorax shape for both DIBH and FB plans.

Patient No.	Breast diameter orthoqonal (cm)	Tangential diameter (cm)	Lung diameter orthoqonal (cm)	Central diameter (cm)
Contour-measurements for DIBH-plans
1	8.5	21.2	0.9	22.5
2	5.2	19.5	1.1	21.5
3	4.8	19.1	0.0	17.7
4	5.1	18.7	0.9	20.6
5	5.4	16.4	0.9	21.4
6	7.1	18.3	1.4	19.3
7	6.1	20.4	1.2	25.2
8	7.2	19.2	2.2	21.7
9	5.8	17.8	1.7	21.1
10	5.3	19.8	1.2	20.6
11	6.6	23.6	0.8	24.1
12	8.5	23.9	1.0	25.1
13	9.4	22.5	1.8	21.6
14	8.3	23.7	1.8	23.8
15	8.8	24.0	1.3	23.0
16	5.9	18.5	1.9	19.4
Mean	6.8	20.4	1.3	21.8
Median	6.4	19.7	1.2	21.6
stddev	1.5	2.4	0.5	2.1
Contour-measurements for FB-plans
1	8.7	21.8	0.9	22.0
2	5.0	19.5	0.8	20.3
3	6.8	198	0.8	18.0
4	5.4	19.1	0.8	19.3
5	5.1	16.7	0.7	20.0
6	6.7	18.3	0.8	18.4
7	6.1	20.0	1.1	23.7
8	6.5	19.6	1.3	20.0
9	5.7	18.0	1.7	18.9
10	5.4	20.3	1.0	19.7
11	6.8	23.8	0.9	23.4
12	8.4	23.6	0.6	23.7
13	9.4	22.6	1.4	20.4
14	8.2	23.5	1.5	23.2
15	8.7	23.5	0.7	22.5
16	5.4	18.7	1.7	18.3
Mean	6.8	20.6	1.0	20.7
Median	6.6	19.9	0.9	20.2
stddev	1.5	2.3	0.4	2.0

Table III. Mean dose for three organs at risk and ERR estimated with linear and non-linear risk models for DIBH and FB plans in 16 breast cancer patients. Individual differential DVHs and mean CB dose are used to calculate ERR with non-linear and lineal model. Following parameter values are employed in risk estimations with non-linear model; α1/ß1 and α2/ß2 = 2 Gy, α1 = 0.002 Gy-1 and α2 = 0.25 Gy-1.

Patient No.	Heart mean dose (Gy)	Lung mean dose (Gy)	ERR for CB Linear model	ERR for CB Non-linear model
DIBH-plans
1	1.7	9.5	0.1	0.2
2	1.7	12.3	0.2	0.2
3	2.1	14.5	0.1	0.2
4	3.0	12.9	0.1	0.1
5	4.2	11.7	0.6	0.2
6	1.6	9.5	0.1	0.1
7	1.5	8.1	0.1	0.1
8	1.5	12.6	0.3	0.1
9	1.6	12.4	0.1	0.1
10	2.1	11.8	0.1	0.1
11	2.1	13.2	0.2	0.2
12	2.1	12.4	0.0	0.1
13	2.2	13.5	0.0	0.1
14	9.4	15.8	0.1	0.1
15	1.9	12.1	0.0	0.1
16	1.4	11.1	0.1	0.1
Mean	2.51	12.09	0.14	0.14
Median	2.00	12.35	0.09	0.13
std	1.97	1.91	0.13	0.04
FB-plans
1	4.8	12.6	0.2	0.2
2	2.4	14.3	0.2	0.1
3	19.1	14.9	0.2	0.3
4	5.1	13.3	0.0	0.1
5	6.4	13.4	0.3	0.2
6	4.2	9.8	0.0	0.1
7	3.9	10.4	0.1	0.1
8	2.2	15.3	0.0	0.1
9	2.8	15.4	0.1	0.1
10	7.7	11.9	0.1	0.1
11	3.4	13.2	0.4	0.1
12	4.9	15.8	0.0	0.1
13	10.9	13.8	0.0	0.2
14	14.9	13.3	0.1	0.1
15	6.9	17.0	0.0	0.1
16	4.9	14.6	0.1	0.1
Mean	6.53	13.69	0.12	0.15
Median	4.90	13.60	0.09	0.13
std	4.70	1.91	0.11	0.05

Figure 2. The reduced lung and cardiac and increased medial sternum dose as a result of decreased lung density in DIBH plan (upper panel) compared to the FB plan (lower panel).