Accelerated partial breast irradiation (APBI): Are breath-hold and volumetric radiation therapy techniques useful?

Figures & data

Table I. Comparison of population averaged PTV dose parameters from different planning techniques (3D-CRT and VMAT) in free-breathing (FB) and in vmDIBH (voluntary moderate deep inspiration breath hold) for the 21 patients with 2 CT scans and 4 different plans.

	3D-CRT	3D-CRT	VMAT	VMAT
	FB	vmDIBH	FB	vmDIBH
Volume (cm^3)	176.4 (49–483)	176.6 (50–483)	176.4 (49–483)	176.6 (50–483)
Dmean (Gy)	38.9 (38.3–39.8)	38.9 (38.4–39.7)	39.2 (38.5–39.6)	39.2 (39.0–39.5)
V95% (%)	96.4 (95.0–100)**	96.1 (92.9–99.9)**	98.9 (97.6–100)	99.1 (97.3–100)
D1% (%)	104 (101–109)**	104 (101–109)**	107 (105–111)	107 (105–110)
CI	1.52 (1.30–1.81)**	1.47 (1.28–1.95)**	1.25 (1.08–1.41)	1.23 (1.16–1.39)

CI, conformity index; D_1%, near-maximum dose = highest dose given to 1% of the PTV, in % of prescribed dose; V_95%, the fraction of the volume receiving ≥ 95% of the prescribed dose.

* Significantly different from VMAT(vmDIBH), ** also significantly different from VMAT(FB).

Table II. Comparison of number of monitor units (MU), ipsilateral lung volumes, and organs at risk dose parameters from different planning techniques (3D-CRT and VMAT) in free-breathing (FB) and breath-hold (vmDIBH), averaged for the 21 patients with 2 CT scans and four different plans.

	3D-CRT FB	3D-CRT vmDIBH	VMAT FB	VMAT vmDIBH
MU	521 (476–617)	528 (497–611)	862 (700–1065)	843 (701–1065)
Ipsilateral breast (non-PTV)
V50% (%)	23.2 (9.8–36.9)**	23.0 (8.0–39.9)**	19.7 (8.2–30.2)	18.0 (2.9–27.0)
V5Gy (%)	48 (23–91)	51 (23–91)	46 (21–92)	47 (21–89)
Heart
DMax (Gy)	19.8 (0.8–38.3)**	11.2 (0.6–38.6)*	14.3 (0.5–39.7)*	8.5 (0.6–30.9)
DMean (Gy)	2.0 (0.1–5.1)**	1.0 (0.1–4.6)	1.0 (0.1–3.3)*	0.6 (0.1–1.6)
V5Gy (%)	15.9 (0.0–46.9)**	7.6 (0.0–39.3)*	4.3 (0.0–47.7)*	1.4 (0.0–8.1)
Contralateral breast
DMax (Gy)	0.7 (0.04–5.8)**	0.4 (0.1–1.4)**	4.6 (0.1–9.4)	4.3 (0.6–8.3)
DMean (Gy)	0.05 (0.01–0.08)**	0.05 (0.01–0.08)**	0.6 (0.03–1.6)	0.6 (0.03–1.9)
Ipsilateral lung
Volume (cm^3)	1311 (809–1920)*	2125 (1408–2727)	1311 (809–1920)*	2125 (1408–2727)
DMean (Gy)	3.7 (0.7–8.7)**	3.4 (1.2–8.0)**	1.9 (0.4–5.5)	1.8 (0.5–4.0)
V5Gy (%)	31.2 (18.7–73.8)**	27.4 (15.0–67.3)**	10.4 (0.0–40.3)	10.6 (0.0–30.8)
Contralateral lung
DMax (Gy)	2.1 (0.1–8.1)**	2.9 (0.2–12.5)*	4.2 (0.5–15.0)	5.0 (0.3–10.5)
DMean (Gy)	0.1 (0.01–1.1)**	0.1 (0.01–1.2)**	0.4 (0.02–1.9)	0.4 (0.02–1.0)

3D-CRT, three-dimensional conformal radiation therapy; FB, free-breathing; vmDIBH, voluntary moderately deep inspiration breath-hold; V_x, the volume of the organ receiving × Gy; V_y%, the volume receiving y% of the prescribed dose. D_max and D_mean are the maximum and mean dose values to an organ.

* Significant difference with VMAT(vmDIBH); ^** Also significant difference with VMAT(FB).

Figure 1. Mean heart dose reduction compared with the 3D-CRT(FB) technique as a result of 3D-CRT(vmDIBH) (×), VMAT(FB) (×) and VMAT(vmDIBH) (×) as a function of the mean heart dose for 3D-CRT(FB) for the 21 patients with 2 CT scans and 4 treatment plans.

Figure 2. Mean heart dose reduction of the VMAT plans compared with the with 3D-CRT plans, for centrally located tumors (×), and tumors located in the upper inner(×), lower inner (×), upper outer (×) and lower outer (×) quadrant of the breast, for all 37 patients in FB and in vmDIBH.

Figure 3. Mean heart dose reduction with VMAT compared with the 3D-CRT plans, in FB (×, solid trendline with right equation) and in vmDIBH (×, dashed trendline with left equation), for all 37 patients in FB and in vmDIBH.