Radiation during deep inspiration allows loco-regional treatment of left breast and axillary-, supraclavicular- and internal mammary lymph nodes without compromising target coverage or dose restrictions to organs at risk

Figures & data

Figure 1. A typical DIBH breathing curve from CT-scanning, with gaps of FB between each DIBH. The CT-scan was acquired during one DIBH (pink area) and the gating window (green lines) was set to the mean amplitude ± 1 mm. CT, computed tomography; DIBH, deep inspiration breath-hold; FB, free breathing.

Table I. Mean volume, in cm³, for planning target volume (PTV) and organs at risk (OAR) during free breathing (FB) and deep inspiration breath-hold (DIBH) for all 17 patients. Data are shown as mean values with one standard deviation, and range in brackets.

	FB	DIBH	p-value
PTV	1362.8 ± 374.7 [843.4–2105.9]	1346.4 ± 365.0 [879.4–2074.0]	0.163
Heart	616.5 ± 75.5 [460.7–750.7]	559.8 ± 72.2 [458.1–676.0]	0.003*
LAD coronary artery	1.0 ± 0.6 [0.2–2.5]	1.0 ± 0.4 [0.6–1.8]	0.253
Ipsilateral lung	1178.2 ± 343.2 [630.0–1978.6]	2165.1 ± 509.9 [1229.3–3249.7]	< 0.001*
Total lung	2635.2 ± 693.4 [1482.3–4246.6]	4676.3 ± 1010.9 [2634.7–6763.8]	< 0.001*
Contralateral breast	631.5 ± 295.2 [252.9–1282.4]	627.4 ± 303.3 [250.1–1298.1]	0.301

LAD, left anterior descending.

*Significant difference (p < 0.05) between FB and DIBH.

Figure 2. CTV (translucent green), mammary tissue (pink) and ipsilateral lung (yellow) for the same patient during FB (left) and DIBH (right). The yellow line shows the craniocaudal position of the isocenter. The white arrows show the measured distances from isocenter to the caudal limit of the internal mammary nodes (A), from isocenter to the cranial limit of CTV (B), from isocenter to cranial limit of the ipsilateral lung (C), as well as the distance from isocenter to the cranial limit of the mammary tissue (D). CTV, clinical target volume; DIBH, deep inspiration breath-hold; FB, free breathing.

Figure 3. The upper panel shows the dose distribution in a transversal CT slice obtained at the same position of PTV for the same patient during FB (left panel) and DIBH (right panel), respectively. The heart moves out of the high dose region during DIBH. The lower panel shows beam's eye views of the medial tangential field during FB (left) and DIBH (right) for the same patient as upper panel. During inspiration the lung volume (blue) is increased, the breast (red) is moved cranioventrally and the heart (pink) caudally. In the shown case, the heart and the LAD coronary artery (green) was not included in the beam portal (yellow lines) during DIBH. CT, computed tomography; DIBH, deep inspiration breath-hold; FB, free breathing; LAD, left anterior descending; PTV, planning target volume.

Figure 4. Mean DVHs averaged for all 17 patients for PTV and OAR with FB (solid line) and DIBH (dotted line). DIBH, deep inspiration breath-hold; DVH, dose-volume histograms; FB, free breathing; OAR, organs at risk; PTV, planning target volume.

Table II. Summary of treatment planning data for PTV and OAR for the 17 breast cancer patients included in this study, with FB and DIBH. The prescription dose was 50 Gy in 2 Gy fractions. For comparison with earlier studies maximum doses are also shown.

	FB	DIBH	p-value
PTV
Mean (Gy)	50.5 ±0.3 [50.0–50.9]	50.5 ±0.3 [50.0–51.0]	0.122
STD (%)	2.6 ± 0.2 [2.2–3.1]	2.7 ± 0.2 [2.4–3.1]	0.022*
Maximum (Gy)	54.0 ±0.3 [53.4–54.4]	54.3 ±0.3 [53.8–55.0]	0.001*
D2% (Gy)	53.0 ±0.3 [52.3–53.5]	53.2 ±0.4 [52.5–53.7]	0.006*
D98% (Gy)	47.8 ±0.2 [47.5–48.2]	47.8 ±0.3 [47.5–48.4]	0.679
V95% (%)	98.9 ±0.5 [98.1–99.7]	98.8 ±0.5 [98.0–99.4]	0.868
Homogeneity index	0.10 ±0.01 [0.09–0.12]	0.11 ±0.01 [0.09–0.12]	0.055
Conformity index	0.99 ±0.00 [0.98–1.00]	0.99 ±0.00 [0.98–0.99]	0.868
Healthy tissues conformity index	0.64 ±0.04 [0.58–0.71]	0.62 ±0.04 [0.57–0.70]	0.006*
Heart
Mean (Gy)	6.2 ±3.6 [2.5–14.4]	3.1 ± 1.9 [1.8–9.7]	<0.001*
Maximum (Gy)	47.4±4.1 [33.5–51.3]	33.5± 13.9 [5.1–49.9]	<0.001*
D2% (Gy)	34.1 ± 14.2 [7.0–48.8]	13.1 ±11.9 [3.7–46.2]	<0.001*
V25Gy (%)	6.7 ± 6.8 [0.1–23.0]	1.2 ± 2.8 [0.0–11.5]	<0.001*
Number of patients with	8 (47.1%)	1 (5.9%)
V25Gy>5%
Median V25Gy (%)	4.8	0.1
MHD^a (cm)	1.9 ± 0.9 [0.9–3.7]	0.7 ± 0.9 [0.0–3.4]	0.001*
Number of patients with	0 (0.0%)	7 (41.2%)
MHD = 0
LAD coronary artery
Mean (Gy)	25.0 ±14.0 [3.7–48.2]	10.9 ±9.1 [3.1–38.9]	<0.001*
Maximum (Gy)	41.0 ±13.0 [5.4–50.3]	27.1 ± 16.7 [4.2–48.4]	0.001*
D2% (Gy)	39.2± 14.0 [5.1–50.1]	24.1 ± 16.3 [4.0–47.8]	0.001*
V25Gy (%)	48.4 ±36.1 [0.0–99.9]	14.1 ±22.8 [0.0–84.7]	0.001*
Ipsilateral lung
Mean (Gy)	21.7 ±2.5 [17.2–24.9]	16.4 ±2.3 [12.6–21.0]	<0.001*
V20Gy (%)	44.5 ±5.0 [35.8–51.2]	32.7 ±4.8 [24.5–41.8]	<0.001*
Median V25Gy (%)	42.8	30.4
MLD^b of medial field (cm)	4.7 ± 0.6 [3.8–5.8]	5.1 ± 0.6 [4.2–6.0]	0.017*
Number of patients with	17 (100%)	6 (35.3%)
V20Gy>35%
Total lung
Mean (Gy)	10.3 ±1.2 [8.4–12.1]	8.1 ± 1.1 [6.5–10.7]	<0.001*
Contralateral breast
Mean (Gy)	2.2 ± 1.7 [0.8–7.5]	2.7 ± 2.0 [1.1–8.7]	0.012*
Maximum (Gy)	40.1 ± 16.8 [11.8–54.8]	44.3± 14.7 [11.1–54.6]	0.587
D2% (Gy)	13.2 ±11.8 [2.5–46.5]	16.5 ±12.4 [3.5–49.0]	0.047*
V2Gy (%)	22.2 ±16.1 [4.2–58.8]	26.1 ± 16.4 [7.6–63.0]	0.049*

DIBH, deep inspiration breath-hold; FB, free breathing; OAR, organs at risk; PTV, planning target volume.

Data are shown as mean values with one standard deviation, and range in brackets, except for the median values.

^aMaximum heart distance.

^bMaximum lung distance.

*Significant difference (p<0.05) between FB and DIBH.

Figure 5. Volume of heart (in %) receiving 25 Gy or more (V25Gy) in FB plans versus DIBH plans plotted for each patient individually. DIBH, deep inspiration breath-hold; FB, free breathing.

Figure 6. Volume of ipsilateral lung (in %) receiving 20 Gy or more (V20Gy) in FB plans versus DIBH plans plotted for each patient individually. DIBH, deep inspiration breath-hold; FB, free breathing.