基于每日CBCT的乳腺癌术后单周超大分割全乳放疗的位置误差及外扩边界研究

doi:10.19401/j.cnki.1007-3639.2025.08.003

摘要/Abstract

摘要：

背景与目的： 乳腺癌保乳术后单周超大分割全乳放疗能在保证疗效和安全性的同时缩短疗程，是目前可选的全乳放疗方案。超大分割放疗要求患者每日接受图像引导，但其对位置误差的影响尚不明确。在每日锥形束计算机断层扫描（cone-beam computed tomography，CBCT）引导下，本研究旨在探索单周超大分割全乳放疗的位置误差及其影响因素，并计算临床靶体积（clinical target volume，CTV）外扩至计划靶体积（planning target volume，PTV）的三维边界。方法： 纳入2021年2月—10月于上海瑞金医院入组乳腺癌术后单周超大分割全乳放疗前瞻性研究（NCT04926766）连续入组的患者的临床资料[（2020）临伦审第（352）号]。所有患者每日治疗前摆位后行CBCT1，根据CBCT1纠正误差后再行CBCT2，当次治疗结束后行CBCT3。CBCT1、CBCT2与定位CT的三维位置误差分别为初始、残余分次间误差。CBCT2与CBCT3间的三维位置误差为分次内误差。根据每次治疗的分次间及分次内误差，基于van Herk公式计算CTV外扩至PTV三维边界。结果： 本研究共入组患者34例，收集CBCT图像510例次。每日治疗前CBCT在线位置纠正显著减少三维位置误差（初始分次间误差vs残余分次间误差：前后2.8 mm vs 0.4 mm；头脚1.6 mm vs 0.5 mm；左右1.8 mm vs 0.3 mm；P均<0.001）。对于残余分次间误差，CTV体积较大患者（>402.5 cm³ vs ≤402.5 cm³）在前后方向（0.5 mm vs 0.3 mm，P=0.023）和头脚方向（0.6 mm vs 0.5 mm，P=0.037）更大。对于分次内误差，CTV较大患者（>402.5 cm³ vs ≤402.5 cm³）在前后方向更大（0.5 mm vs 0.2 mm，P=0.001）；身体质量指数（body mass index，BMI）较高患者（>23.2 kg/m² vs ≤23.2 kg/m²）在前后方向更大（0.7 mm vs 0.2 mm，P<0.001）；体重更大患者（> 60.0 kg vs ≤60.0 kg）在前后方向更大（0.5 mm vs 0.2 mm，P=0.033）。每日CBCT引导下CTV外扩至PTV边界推荐为：前后2.3 mm，头脚2.8 mm，左右2.0 mm。但CTV>402.5 cm³和BMI>23.2 kg/m²的患者需要更大的头脚方向外扩边界，分别为3.1和3.4 mm。结论： 每日CBCT图像引导下，对大部分患者将全乳放疗CTV外扩至PTV的三维边界限制在3 mm内是可行的，而BMI较高和CTV较大患者需在头脚方向适度增大外扩边界。

关键词: 乳腺癌, 单周超大分割放疗, 全乳放疗, 位置误差, 外扩边界

Abstract:

Background and purpose: Single-week ultra-hypofractionated whole breast irradiation (WBI) after breast-conserving surgery could shorten the treatment duration while ensuring efficacy and safety, making it a viable option for WBI. However, ultra-hypofractionated WBI requires daily image-guided radiotherapy (IGRT), and its impact on setup errors remains unclear. This study aimed to identify factors associated with set-up errors in ultra-hypofractionated WBI guided with daily cone-beam computed tomography (CBCT) and calculate margin expanded from clinical target volume (CTV) to planning target volume (PTV). Methods: This study included patients enrolled in a prospective trial that explored the safety of single-week ultra-hypofractionated WBI (NCT04926766) in Shanghai Ruijin Hospital, which was approved by Shanghai Ruijin Hospital Ethics Committee (No. 2020-352). All patients received CBCT1 after positioning. After correcting errors, patients received CBCT2. CBCT3 was conducted after radiotherapy was completed. The translational errors between CBCT1, CBCT2, and plan CT were initial and residual inter-fractional errors. The translational error between CBCT2 and CBCT3 was an intra-fractional error. The PTV margin was calculated according to the van Herk formula. Results: A total of 34 patients were enrolled in this study, and 510 CBCT images were collected. Daily CBCT significantly reduced set-up error in anterior-posterior (AP), superior-inferior (SI) and right-left (RL) directions (initial inter-fractional error vs residual inter-fractional error: AP, 2.8 mm vs 0.4 mm; SI, 1.6 mm vs 0.5 mm; RL, 1.8 mm vs 0.3 mm, all P<0.001). Higher CTV volume (>402.5 cm³ vs ≤402.5 cm³) was associated with larger residual inter-fractional error (0.5 mm vs 0.3 mm, P=0.023) and intra-fractional error (0.5 mm vs 0.2 mm, P=0.001) in AP direction. Higher CTV volume was also associated with larger residual inter-fractional error in the SI direction (0.6 mm vs 0.5 mm, P=0.037). Higher BMI (>23.2 kg/m² vs ≤23.2 kg/m²) and larger weight (>60.0 kg vs ≤60.0 kg) were associated with larger intra-fractional error in AP direction: 0.7 mm vs 0.2 mm (P <0.001) and 0.5 mm vs 0.2 mm (P=0.033), respectively. Under guidance with daily CBCT, the recommended margins were 2.3 mm in AP direction, 2.8 mm in SI direction, and 2.0 mm in RL direction. However, in patients with CTV volume >402.5 cm³ and BMI>23.2 kg/m², a larger margin was recommended in SI direction: 3.1 mm and 3.4 mm, respectively. Conclusion: The 3 mm margin was feasible under guidance with daily CBCT. The CTV to PTV margin should be larger in patients with higher BMI or CTV volume.

Key words: Breast cancer, Ultra-hypofractionated radiotherapy, Whole breast irradiation, Set-up error, Margin

中图分类号:

R737.9

王孟潇, 樊文栋, 曹菁璟, 陈佳艺, 蔡钢, 曹璐. 基于每日CBCT的乳腺癌术后单周超大分割全乳放疗的位置误差及外扩边界研究[J]. 中国癌症杂志, 2025, 35(8): 752-760.

WANG Mengxiao, FAN Wendong, CAO Jingjing, CHEN Jiayi, CAI Gang, CAO Lu. Set-up error and CTV margin in one-week ultra-hypofractionated whole breast irradiation after breast-conserving surgery based on daily CBCT[J]. China Oncology, 2025, 35(8): 752-760.

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参考文献 18

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Characteristics	Patients (n=34)
Age median (range)/year	53.5 (40.0, 74.0)
CTV volume median (range)/cm³	402.5 (143.2, 958.6)
Height median (range)/cm	161.5 (150.0, 168.0)
Weight median (range)/kg	60.0 (45.0, 78.0)
BMI median (range)/ (kg·m^-2)	23.2 (18.0, 28.0)
Laterality n(%)
Left	22 (64.7)
Right	12 (35.3)
Quadrant n(%)
Upper inner	6 (17.6)
Lower inner	4 (11.8)
Upper outer	20 (58.8)
Lower outer	4 (11.8)
Axillary surgery n(%)
Sentinel lymph node biopsy	32 (94.1)
None	2 (5.9)
Pathological tumor stage n(%)
pTis	6 (17.6)
pT1	24 (70.6)
pT2	4 (11.8)
Pathological nodal stage n(%)
pNx	2 (5.9)
pN0	31 (91.2)
pN1mi	1 (2.9)
Subtype n(%)
HR⁺/HER2⁺	2 (5.9)
HR⁺/HER^2-	27 (79.4)
HR^-/HER2⁺	1 (2.9)
HR^-/HER2^-	4 (11.8)
Adjuvant therapy n(%)
None	19 (55.8)
Chemotherapy	12 (35.3)
Chemotherapy+anti-HER2 therapy	3 (8.8)

	AP/mm			SI/mm			RL/mm
	Median (range)	Z value^a/ H value^b	P value	Median (range）	Z value/ H value	P value	Median (range)	Z value/ H value	P value
Age/year		-0.818	0.414		-0.335	0.738		-0.003	0.997
≤53.5	0.5 (0.0, 2.1)			0.5 (0.0, 2.1)			0.3 (0.0, 2.6)
>53.5	0.4 (0.0, 2.4)			0.5 (0.2, 2.0)			0.3 (0.0, 1.9)
CTV/cm³		-2.265	0.023		-2.083	0.037		-1.587	0.112
≤402.5	0.3 (0.0, 2.4)			0.5 (0.0, 2.0)			0.4 (0.0, 2.6)
>402.5	0.5 (0.0, 2.1)			0.6 (0.0, 2.1)			0.2 (0.0, 1.9)
Height/cm		-2.206	0.027		-0.770	0.441		-0.480	0.631
≤161.5	0.4 (0.0, 2.1)			0.5 (0.0, 2.1)			0.2 (0.0, 2.6)
>161.5	0.4 (0.0, 2.4)			0.5 (0.0, 2.0)			0.3 (0.0, 1.9)
Weight/kg		-0.839	0.401		-0.804	0.421		-0.710	0.478
≤60.0	0.4 (0.0, 2.4)			0.5 (0.0, 2.1)			0.4 (0.0, 2.6)
>60.0	0.5 (0.0, 2.1)			0.5 (0.0, 1.9)			0.2 (0.0, 1.9)
BMI/(kg·m^-2)		-0.252	0.801		-1.701	0.089		-0.848	0.396
≤23.2	0.4 (0.0, 2.4)			0.5 (0.0, 2.0)			0.4 (0.0, 2.6)
>23.2	0.4 (0.0, 2.1)			0.5 (0.0, 2.1)			0.3 (0.0, 1.9)
Laterality		-0.987	0.324		-1.299	0.194		-1.520	0.129
Left	0.4 (0.0, 2.1)			0.5 (0.0, 1.9)			0.3 (0.0, 2.6)
Right	0.6 (0.0, 2.4)			0.5 (0.1, 2.1)			0.4 (0.0, 1.9)
Quadrant		1.862	0.601		7.222	0.065		2.754	0.431
Upper inner	0.5 (0.0, 2.4)			0.5 (0.0, 2.0)			0.4 (0.0, 2.6)
Lower inner	0.5 (0.0, 1.3)			0.8 (0.1, 1.8)			0.2 (0.0, 0.9)
Upper outer	0.4 (0.0, 2.1)			0.5 (0.0, 2.1)			0.4 (0.0, 1.9)
Lower outer	0.4 (0.1, 2.1)			0.8 (0.0, 1.9)			0.3 (0.0, 1.0)
Adjuvant therapy		-1.495	0.135		-1.414	0.157		-0.370	0.711
None	0.4 (0.0, 2.1)			0.5 (0.0, 2.1)			0.3 (0.0, 2.6)
Yes	0.5 (0.0, 2.4)			0.6 (0.0, 2.0)			0.3 (0.0, 1.4)

Item	AP/mm			SI/mm			RL/mm
Item	Median (range)	Z value^a/ H value^b	P value	Median (range)	Z value/ H value	P value	Median (range)	Z value/ H value	P value
Age/year		-1.109	0.267		-0.713	0.476		-0.743	0.457
≤53.5	0.2 (0.0, 3.9)			0.8 (0.0, 4.4)			0.5 (0.0, 3.1)
>53.5	0.4 (0.0, 2.6)			0.6 (0.0, 3.0)			0.2 (0.0, 2.8)
CTV/cm³		-3.308	0.001		-1.286	0.198		-1.156	0.248
≤402.5	0.2 (0.0, 2.4)			0.5 (0.0, 4.4)			0.2 (0.0, 3.1)
>402.5	0.5 (0.0, 3.9)			0.9 (0.0, 3.5)			0.4 (0.0, 2.5)
Height/cm		-1.329	0.184		-0.347	0.729		-0.555	0.579
≤161.5	0.2 (0.0, 3.9)			0.6 (0.0, 4.4)			0.3 (0.0, 3.1)
>161.5	0.4 (0.0, 2.6)			0.7 (0.0, 3.5)			0.3 (0.0, 2.2)
Weight/kg		-2.129	0.033		-0.461	0.645		-0.597	0.550
≤60.0	0.2 (0.0, 3.9)			0.7 (0.0, 4.4)			0.3 (0.0, 3.1)
>60.0	0.5 (0.0, 2.6)			0.6 (0.0, 3.5)			0.5 (0.0, 1.9)
BMI/(kg·m^-2)		-3.506	<0.001		-1.624	0.104		-1.501	0.133
≤23.2	0.2 (0.0, 2.3)			0.5 (0.0, 3.5)			0.3 (0.0, 3.1)
>23.2	0.7 (0.0, 3.9)			0.8 (0.0, 4.4)			0.5 (0.0, 2.5)
Laterality		-0.350	0.726		-1.571	0.116		-1.692	0.091
Left	0.3 (0.0, 2.5)			0.6 (0.0, 3.0)			0.6 (0.0, 3.1)
Right	0.3 (0.0, 3.9)			0.9 (0.0, 4.4)			0.2 (0.0, 2.8)
Quadrant		1.336	0.721		10.375	0.016		7.106	0.069
Upper inner	0.2 (0.0, 1.1)			0.3 (0.0, 2.4)			0.2 (0.0, 2.2)
Lower inner	0.2 (0.0, 2.4)			1.3 (0.0, 4.4)			0.3 (0.0, 1.5)
Upper outer	0.3 (0.0, 3.9)			0.5 (0.0, 3.0)			0.5 (0.0, 3.1)
Lower outer	0.3 (0.0, 2.2)			0.9 (0.0, 3.0)			0.9 (0.0, 1.9)
Adjuvant therapy		-0.297	0.766		-1.841	0.066		-0.224	0.823
None	0.2 (0.0, 3.9)			0.8 (0.0, 4.4)			0.3 (0.0, 3.1)
Yes	0.4 (0.0, 2.3)			0.3 (0.0, 3.5)			0.3 (0.0, 2.2)

Item	Margin without daily CBCT/mm			Margin with daily CBCT/mm
Item	AP	SI	RL	AP	SI	RL
Overall cohort (n=34)	8.9	7.2	7.1	2.3	2.8	2.0
Categorized by BMI
≤23.2kg/m² (n=17)	9.0	6.3	5.6	1.8	2.3	2.0
>23.2kg/m² (n=17)	8.6	7.9	8.4	2.6	3.4	2.0
Categorized by height
≤161.5 cm (n=17)	8.6	4.6	6.8	2.2	2.7	2.3
>161.5 cm (n=17)	9.2	8.6	7.5	2.3	2.9	1.8
Categorized by weight
≤60.0 kg (n=19)	8.7	6.2	6.0	2.2	2.7	2.2
>60.0 kg (n=15)	9.2	8.2	8.2	2.4	2.9	1.7
Categorized by CTV
≤402.5 cm³ (n=17)	6.8	6.4	5.9	1.6	2.6	2.1
>402.5 cm³ (n=17)	10.1	8.0	8.2	2.8	3.1	2.0
Categorized by quadrant
Upper inner quadrant (n=6)	6.5	5.5	5.1	1.8	2.2	2.0
Lower inner quadrant (n=4)	10.7	5.8	4.5	1.8	2.5	1.8
Upper outer quadrant (n=20)	9.1	7.7	7.5	2.2	2.6	2.1
Lower outer quadrant (n=4)	7.3	7.8	7.5	2.9	4.2	2.1