Dosimetric risk factors for radiation esophagitis in patients with breast cancer following regional nodal radiation

Table 1 Patient characteristics

Variable	G0	G2	χ2	P value
Age
< 60	41	7	0.92	0.57
≥ 60	12	4
Laterality
Left	28	5	0.20	0.66
Right	25	6
Type of surgery
Mastectomy	40	6	1.97	0.16
Lumpectomy	13	5
Histologic type
Ductal invasive carcinoma	45	11	1.90	0.59
Lobular invasive carcinoma	3	0
Mucinous carcinoma	2	0
Others	3	0
Stage group
Ⅱ A	31	6	2.12	0.35
Ⅱ B	10	4
Ⅲ	12	1
Molecular subtype
Luminal A	18	2	6.389	0.172
Luminal B	8	0
Luminal HER2-positive	9	1
HER2 overpressing	6	2
Triple-negative	12	6
Chemotherapy
Neoadjuvant chemotherapy	19	5	0.69	0.71
Adjuvant chemotherapy	32	6
No chemotherapy	2	0
Anti-HER2 targeted therapy
No	37	9	0.65	0.66
Yes	15	3

G0: No radiation oesophagitis; G2: Grade 2 radiation oesophagitis; HER2: Human epidermal growth factor receptor 2.

Table 2 Univariable logistic regression analyses of clinical characteristics and grade 2 radiation oesophagitis

Variable	OR (95%CI)	P value
Age
< 60	1.00	0.34
≥ 60	1.95 (0.49-7.81)
Laterality
Left	1.00
Right	1.34 (0.37-4.95)	0.66
Surgery
Lumpectomy	1.00
Mastectomy	0.39 (0.10-1.49)	0.17
Histologic type
Ductal invasive carcinoma	1.00
Others	0.00 (0.00-)	1.0
Stage
Ⅱ	1.00
Ⅲ	0.34 (0.04-2.94)	0.33
Anti-HER2 targeted therapy
Yes	1.00
No	1.05 (0.25-4.51)	0.95
Chemotherapy
Yes	1.00
No	0.00(0.00- )	1.0

OR: Odds ratio; CI: Confidence interval; HER2: Human epidermal growth factor receptor 2.

Table 3 Degree of variability of dosimetric parameters in patients

Variable	G0			≥ G2
	Mean	Range	Std Dev	Mean	Range	Std Dev
Total volume	8.59	(6.01-11.75)	1.28	8.90	(6.65-11.19)	1.40
Dmax	39.60	(34.35-46.38)	3.24	42.78	(39.40-46.81)	2.69
Dmean	16.11	(10.5-25.28)	3.02	19.44	(14.30-22.49)	2.71
RV V10 (%)	59.35	(28.83-87.50)	16.41	66.45	(37.87-95.19)	17.45
RV V20 (%)	37.62	(19.45-71.20)	10.09	45.27	(31.06-54.15)	7.26
RV V30 (%)	16.45	(5.10-38.69)	8.81	36.45	(26.28-44.83)	5.81
RV V35 (%)	4.59	(0.00-27.09)	5.93	17.11	(7.01-27.95)	7.91
RV V40 (%)	0.58	(0.00-9.57)	1.57	3.02	(0.00-11.55)	4.36
AV V10 (mL)	5.10	(2.34-8.97)	1.48	5.73	(3.54-7.34)	1.34
AV V20 (mL)	3.23	(1.42-6.55)	0.96	4.03	(2.51-5.48)	0.91
AV V30 (mL)	1.39	(0.08-2.79)	0.71	3.25	(2.01-4.73)	1.34
AV V35 (mL)	0.37	(0.00-2.03)	0.47	1.49	(0.61-2.33)	0.67
AV V40 (mL)	0.05	(0.00-0.88)	0.14	0.27	(0.00-1.03)	0.40

G0: No radiation oesophagitis; G2: Grade 2 radiation oesophagitis; RV: Relative volume; AV: Absolute volume.

Table 4 Comparisons of esophageal dosimetric parameters between patients without and with grade 2 radiation oesophagitis

Variable	Univariable logistic regression		Stepwise linear regression
	OR (95%CI)	P value	Adjust R2	Std. error	F	P value
Total volume	1.20 (0.72-2.00)	0.48
Dmean	1.44 (1.12-1.85)	< 0.01
Dmax	1.38 (1.09-1.76)	0.01
RV V10	1.02 (0.98-1.06)	0.29
RV V20	1.08 (1.01-1.16)	0.03
RV V30	1.36 (1.13-1.63)	< 0.01
RV V35	1.22 (1.10-1.36)	< 0.01
RV V40	1.36 (1.06-1.75)	0.01
AV V10	1.38 (0.89-2.13)	0.16
AV V20	2.30 (1.14-4.64)	0.02
AV V30	2.97 (1.88-5.69)	< 0.01	0.48	0.48	59.1	< 0.01
AV V35	2.43 (1.45-3.96)	< 0.01	0.51	0.76	33.9	0.03
AV V40	2.52 (1.96-3.60)	0.01

OR: Odds ratio; CI: Confidence interval; RV: Relative volume; AV: Absolute volume.