The potential benefits from respiratory gating for breast cancer patients regarding target coverage and dose to organs at risk when applying strict dose limits to the heart: results from the DBCG HYPO trial

Figures & data

Table 1. Patient characteristics in the normo- and hypofractionated arm.

Characteristic	Normofractionated			Hypofractionated
	Right-sided	Left-sided		Right-sided	Left-sided
	FB	FB	RG	FB	FB	RG
No. of patients	354	176	199	345	176	192
Age (years)	58	60	60	59	59	59
	50–67	53–68	51–58	50–68	51–68	51–67
	42–83	42–80	42–83	41–77	41–82	42–75
CTVp_breast volume (mL)	617	697	602	619	661	613
	328–1072	340–1105	339–997	313–1138	336–1163	305–1011
	86–3041	69–2501	74–2467	97–2454	98–2164	90–2624
Heart volume (mL)	625	582	594	628	610	601
	521–720	481–699	508–710	513–751	491–733	512–714
	333–980	376–1027	346–1132	341–932	396–1137	334–931
Ipsilateral lung volume (mL)	1542	1219	2170	1544	1226	2233
	1257–1906	961–1572	1756–2598	1255–1922	994–1559	1843–2564
	757–2790	703–2613	1026–3642	917–2890	626–2682	833–3316

Values presented are median, interpercentile range (0.16–0.84) and range.

Table 2. Median values, interpercentile range (0.16–0.84) and range for dose optimization parameters in the normo- and hypofractionated arm.

Parameter	Normofractionated			Hypofractionated
	Right	Left		Right	Left
	FB	FB	RG	FB	FB	RG
CTVp_breast V95% (%)	94.6	92.6	94.7	94.6	91.8	94.4
	92.6–97.1	88.4–95.4	92.6–97.2	92.6–96.4	87.0–94.9	91.7–96.6
	70.6–99.1	72.0–99.3	81.4–99.7	79.4–99.4	80.0–98.7	76.8–99.0
	p = .78	p < .001	–	p = .50	p < .001	–
LADCA Dmax (Gy)	0.6	112.9	12.6	0.4	11.8	11.0
	0.2–1.1	10.2–18.0	7.9–20.4	0.2–0.9	8.7–15.4	6.1–18.0
	0.1–26.3	0.5–48.0	2.2–29.5	0.0–19.7	0.18–39.3	2.4–32.0
	p < .001	p = .56	–	p < .001	p = .22	–
Lung MLD (Gy)	9.0	8.3	7.3	7.3	6.4	5.8
	7.0–10.9	6.2–10.3	5.7–9.0	5.6–9.0	4.9–8.3	4.6–7.2
	3.1–15.7	3.3–12.2	2.9–11.7	3.0–11.2	3.0–10.1	2.5–9.4
	p < .001	p < .001	–	p < .001	p < .001	–
Lung	16.7	15.3	13.6	16.4	14.6	12.7
V20Gy (%) (normo)	12.2–21.0	10.7–19.8	9.9–17.2	12.0–21.1	10.4–19.5	9.7–16.4
V17Gy (%) (hypo)	4.2–32.0	3.7–24.1	2.0–22.8	4.7–27.2	5.3–23.0	3.3–23.1
	p < .001	p < .001	–	p < .001	p < .001	–
Heart MHD (Gy)	0.7	1.8	1.5	0.6	1.5	1.2
	0.4–1.0	1.4–2.5	1.1–1.9	0.3–0.8	1.1–2.0	0.8–1.6
	0.2–2.4	0.4–9.2	0.5–3.5	0.2–2.9	0.3–4.2	0.4–4.7
	p < .001	p < .001	–	p < .001	p < .001	–
Heart	0.0	0.4	0.1	0.0	0.3	0.1
V20Gy (%) (normo)	0.0–0.0	0.0–1.6	0.0–0.5	0.0–0.0	0.0–1.2	0.0–0.5
V17Gy (%) (hypo)	0.0–0.8	0.0–8.4	0.0–4.1	0.0–1.1	0.0–7.0	0.0–8.9
	p < .001	p < .001	–	p < .001	p < .001	–
Heart	0.0	0.0	0.0	0.0	0.0	0.0
V40Gy (%) (normo)	0–0	0.0–0.4	0.0–0.0	0.0–0.0	0.0–0.1	0.0–0.0
V35Gy (%) (hypo)	0.0–0.1	0.0–4.6	0.0–1.4	0.0–0.1	0.0–2.7	0.0–4.6
	p < .001	p < .001	–	p < .001	p < .001	–

V_x% = volume (%) receiving x% of prescribed dose or higher. The p values are based on two-tailed Mann–Whitney U-tests and show whether group distributions differ from RG left-sided patient within each treatment arm.

Figure 1. Box-whisker plots for (top) V_95% for the CTV for both normo- and hypofractionated arm, (middle) MHD for normofractionated arm, and (bottom) MHD for hypofractionated arm. V_x%=volume (%) receiving x% of prescribed dose or higher.

Figure 2. Target coverage of CTV against MHD for FB and RG left-sided patients for (top) normofractionated and (bottom) hypofractionated arm. The solid line indicates the shift of group mean. V_x%=volume (%) receiving x% of prescribed dose or higher.

Figure 3. Box-whisker plots for each centre comparing RG versus FB for (top) target coverage for left-sided patients, (middle) MHD in the normofractionated arm, and (bottom) MHD in the hypofractionated arm. V_x%=volume (%) receiving x% of prescribed dose or higher.