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Table 1 Median (range) and p values of the Mann-Whitney U-test on continuous variables, and percentage and p values of the Pearson’s chi-squared test on categorical variable, in groups with grade 2 and grade 3 skin toxicity

From: Prognostic factors of radiation dermatitis following passive-scattering proton therapy for breast cancer

 

Grade 3

Grade 2

 

Continuous variables

Median (range)

Median (range)

Mann-Whitney U-test p-values

V25CGE (cm3)

257.8 (194.8–330.6)

260.8 (197.7–355.9)

0.93

D150cm3 (CGE)

46.6 (40–48.9)

46.7 (40.4–49.1)

0.69

D100cm3 (CGE)

49.5 (46.4–50.7)

48.9 (46.8–50.3)

0.19

D30cm3 (CGE)

52.1 (49.3–53.9)

51.5 (50.0–52.1)

0.07

D10cm3 (CGE)

53.1 (51.2–55.2)

52.2 (50.7–53.0)

0.03

V50CGE (cm3)

83.0 (22.7–119.8)

68.3 (20.1–114.7)

0.28

V47.5CGE (cm3)

140.3 (76.9–173.8)

118.5 (91.8–168.6)

0.13

V52.5CGE (cm3)

20.7 (0.4–63.3)

5.2 (0–21.0)

0.03

breast volume (cm3)

796.5 (287.2–1746.1)

928.8 (221.7–1328.9)

0.31

planning target volume (cm3)

1224.3 (644.8–2394.0)

1166.0 (490.5–1760.7)

0.64

body mass index

28.7 (23.8–52.1)

29.4 (21.9–47.2)

0.83

age (years)

64 (10)

60 (11)

0.66

Categorical variables

Percentage

Percentage

Pearson’s chi-squared test p-values

history of smoking

80.0%

30.8%

0.02

existence of diabetes

30.0%

23.1%

0.71

  1. Statistical significance is indicated in bold
  2. Abbreviations: CGE cobalt gray equivalent