Radiation dose to the nodal regions during prone versus supine breast irradiation

Figures & data

Figure 1 (A and B) Left-sided whole-breast irradiation. (A) Beam’s eye view of the right anterior oblique field, with 3-D reconstruction of axillary levels I–III and internal mammary lymph-node regions in the prone and supine positions. (B) Typical field arrangements and their relation to the node regions.

Table 1 Volumes of the irradiated breast (PTV) and the nodal regions in the prone and supine positions

Volumes	Prone (mean ± SE, mm^3)	Supine (mean ± SE, mm^3)	P (paired t-test)
PTV	971.6±44.0	967.3±44.4	0.380
Level I	61.6±2.0	62.7±2.2	0.306
Level II	14.2±0.4	13.9±1.2	0.792
Level III	6.0±0.2	5.9±0.2	0.451
IM	4.7±0.1	4.7±0.1	0.450

Note: The volumes of the PTV or the nodal regions did not differ in the prone versus the supine position.

Abbreviations: PTV, planning target volume; SE, standard error; IM, internal mammary.

Table 2 Mean doses to the nodal regions in the prone and supine positions

Volumes	Mean dose ± SE, Gy (range)		P (paired t-test)
	Prone	Supine
Level I	6.6±0.6 (0.6–29.8)	37.7±0.7 (18.6–50.5)	<0.001
Level II	2.1±0.4 (0.6–30.4)	13.8±0.1 (0.7–45.8)	<0.001
Level III	0.5±0.1 (0.1–6.2)	1.6±0.2 (0.3–12.6)	<0.001
IM	6.2±0.6 (1.4–48.9)	15.3±6.2 (2.6–38.7)	<0.001

Note: The mean doses to axillary levels I–III and the internal mammary (IM) lymph nodes were significantly lower in the prone position than in the supine position.

Abbreviation: SE, standard error.

Table 3 Dosimetric values in the nodal regions in the prone and supine positions (P<0.001)

	V25Gy, mean ± SE, % (range)		V45Gy, mean ± SE, % (range)		V47.5Gy, mean ± SE, % (range)
	Prone	Supine	Prone	Supine	Prone	Supine
Level I	9.4±1.3 (0–58.9)	77.3±1.5 (35.1–99.9)	3.0±0.7 (0–39.8)	54.6±2.1 (0.8–97.5)	1.7±0.5 (0–31.7)	40.2±2.2 (0–94.2)
Level II	1.8±0.8 (0–64.2)	24.3±2.6 (0–99.8)	0.4±0.3 (0–28.4)	5.5±1.3 (0–69.0)	0.1±0.1 (0–14.1)	1.9±0.7 (0–49.8)
Level III	0.01±0.0 (0–1.5)	0.6±0.2 (0–17.1)	0	0	0	0
IM	4.9±1.1 (0–60.3)	25.5±2.6 (0–79.9)	0.1±0.1 (0–13.8)	4.9±0.9 (0–60.0)	0.1±0.1 (0–7.0)	2.5±0.7 (0–47.8)

Note: Doses to axillary levels I–III and the internal mammary (IM) lymph nodes were significantly lower in the prone position than in the supine position.

Abbreviation: SE, standard error.