Table 1 Patient characteristics

Family history of breast cancer (MD = 0 and 1)^a

0.77

   Without

42

79

198

77

   With

11

21

58

23

Age (MD = 0 and 0)^a

   Median (min-max) in years

37 (23–40)

37 (23–40)

0.71

   ≤ 35 years old

37

70

176

68

0.85

   > 35 years old

16

30

81

32

Clinical T stage (MD = 0 and 0)^a

0.0496

   cT0–1

31

58

186

72

   cT2

22

42

71

28

Clinical N stage (MD = 0 and 0)^a

0.70

   N0

52

98

246

96

   N1

1

2

11

4

Type of invasive carcinoma (MD = 0 and 0)^a

0.18^b

   Ductal

46

87

223

87

   Lobular

6

11

16

6

   Other

1

2

18

7

Histologic grade (MD = 0 and 1)^a

0.03^b

   1–2

14

26

110

43

   3

36

68

120

47

   Unclassifiable

3

6

26

10

Estrogen receptor (ER) (MD = 6 and 37)^a

0.59

   ER^-

10

21

55

25

   ER⁺

37

79

165

75

Progesterone receptor (PR) (MD = 6 and 39)^a

0.84

   PR^-

9

19

39

18

   PR⁺

38

81

179

82

Hormone receptors (HRs) (MD = 6 and 37)^a

0.87

   HR^-

7

15

35

16

   HR⁺

40

85

185

84

Lymphovascular involvement (MD = 3 and 43)^a

0.0004

   Absent

33

66

188

88

   Present

17

34

26

12

Histologic T stage (MD = 5 and 12)^a

0.89

   pT1

34

71

176

72

   pT2

14

29

69

28

Histologic N stage (MD = 0 and 34)^a

0.06

   pN0

31

58

182

73

   pN1–3

22

42

41

27

Surgical margins (MD = 4 and 10)^a

0.10

   Satisfactory (≥ 3 mm)

32

65

129

52

   Unsatisfactory

17

35

118

48

Systemic therapy (MD = 0 and 0)^a

0.0001

   None

16

30

151

59

   Hormone therapy (HT) only

0

0

101

39

   Chemotherapy ± HT

37

70

5

2

Total RT dose (MD = 0)^a

   Median (min-max) in Gy

66 (50–75)

64 (0–80)

0.14

   < 60 Gy

13

25

101

39

0.043

   ≥ 60 Gy

40

75

156

61