Cardiac dose reduction with deep inspiration breath hold for left-sided breast cancer radiotherapy patients with and without regional nodal irradiation

Table 2 Comparison of average dose parameters for targets and OARs for left-sided breast cancers by treatment cohort

Parameter	WBRT	WBRT FB vs. DIBH p-value*	B/CWRT + RNI	B/CWRT FB vs. DIBH p-value***	All Patients	FB vs. DIBH p-value*
CTV_b Volume (cc)
FB	515.5 ± 356.9	0.577	489.2 ± 200.8	0.496	503.7 ± 290.2	0.349
DIBH	511.8 ± 354.6	0.577	491.3 ± 218.6	0.496	502.6 ± 294.0	0.349
D₉₅ for CTV_b (%)
FB	97.3 ± 1.4	0.286	92.2 ± 8.1	0.030	95.0 ± 5.9	0.013
DIBH	97.7 ± 1.3	0.286	96.2 ± 3.0	0.030	97.0 ± 2.3	0.013
V₈₀ IMC (%)
FB	N/A	N/A	99.7 ± 0.9	1.000	N/A	N/A
DIBH	N/A		98.9 ± 3.3	1.000	N/A	N/A
D_mean Heart (cGy)
FB	166.1 ± 71.0	0.001**	375.7 ± 186.0	0.004**	260.5 ± 169.3	<0.001**
DIBH	110.8 ± 32.1	0.001**	145.0 ± 37.7	0.004**	126.2 ± 38.0	<0.001**
V₂₅ Heart (%)
FB	0.8 ± 1.4	0.059	4.0 ± 3.4	0.014	2.2 ± 2.9	0.002**
DIBH	0.1 ± 0.4	0.059	0.0 ± 0.1	0.014	0.1 ± 0.3	0.002**
D_mean LAD (cGy)
FB	1004.6 ± 892.4	0.002**	1802.8 ± 917.8	0.004**	1363.8 ± 969.4	<0.001**
DIBH	420.0 ± 277.4	0.002**	396.2 ± 81.5	0.004**	409.3 ± 208.4	<0.001**
V₂₀ Left Lung (%)
FB	10.5 ± 4.6	0.067	18.3 ± 5.1	0.250	14.0 ± 6.2	0.029
DIBH	8.5 ± 3.6	0.067	16.3 ± 2.8	0.250	12.0 ± 5.1	0.029
Patients meeting
D_mean < 4Gy (fraction, %)
FB	11/11 (100)	N/A	5/9 (56)	0.134	16/20 (80)	0.134
DIBH	11/11 (100)	N/A	9/9 (100)	0.134	20/20 (100)	0.134

Wilcoxon signed-rank test is used for comparison of all continuous variables, and McNemar's test is applied for discrete variables
Significant p-values after adjusting for multiple testing are indicated by a double asterisk (**)
Abbreviations: WBRT = whole breast RT ± boost cohort, B/CWRT + RNI = breast or chest wall + regional nodal RT cohort, FB = free-breathing, DIBH = deep inspiration breath hold, CTV_b = CTV for breast or chest wall, IMC = internal mammary chain nodes, D₉₅ = Dose to 95 % target volume,V₈₀ = % volume of organ receiving 80 % of the prescription dose, V₂₅ = % volume of organ receiving 25 Gy, D_mean = Mean dose, LAD = left anterior descending coronary artery, V₂₀ = % volume of organ receiving 20 Gy, N/A = not applicable. Data shown are mean values with one standard deviation. *In this group, to achieve significance p-values must be < 0.0083 to account for multiple testing. ***In this group, to achieve significance p-values must be < 0.0071 to account for multiple testing. **Indicates significance when compared to the Bonferroni adjusted criterion

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