Table 1 Demographic and tumor characteristics of patients by age group

 Median (range)

68 (65–94)

68 (65–74)

77 (75–94)

Body mass index (Kg/m²)

 Underweight (<  18.5)

48 (4.4)

33 (3.5)

15 (9.1)

 Normal (18.5–23.9)

440 (40.2)

370 (39.8)

70 (42.7)

 Overweight (24.0–27.9)

310 (28.3)

278 (29.9)

32 (19.5)

 Obese (≥ 28.0)

94 (8.6)

86 (9.2)

8 (4.9)

 Unknown^a

202 (18.5)

163 (17.5)

39 (23.8)

Histology

 DCIS

86 (7.9)

68 (7.3)

18 (11.0)

 IDC

863 (78.9)

739 (79.5)

124 (75.6)

 Other

97 (8.9)

81 (8.7)

16 (9.8)

 Unknown^a

48 (4.4)

42 (4.5)

6 (3.7)

Clinical stage

 0-I

269 (24.6)

223 (24.0)

46 (28.0)

 II

511 (46.7)

441 (47.4)

70 (42.7)

 III

269 (24.6)

230 (24.7)

39 (23.8)

 Unknown^a (I-III)

45 (4.1)

36 (3.9)

9 (5.5)

T stage

  ≤ T1

394 (36.0)

333 (35.8)

61 (37.2)

 T2

525 (48.0)

454 (48.8)

71 (43.3)

 T3-T4

125 (11.4)

103 (11.1)

22 (13.4)

 Unknown^a

50 (4.6)

40 (4.3)

10 (6.1)

N stage

 N0

583 (53.3)

485 (52.2)

98 (59.8)

 N1

302 (27.6)

260 (28.0)

42 (25.6)

 N2

112 (10.2)

103 (11.1)

9 (5.5)

 N3

97 (8.9)

82 (8.8)

15 (9.1)

HR status

 Positive

757 (69.2)

641 (68.9)

116 (70.7)

 Negative

305 (27.9)

260 (28.0)

45 (27.4)

 Unknown^a

32 (2.9)

29 (3.1)

3 (1.8)

HER2 status

 Positive

153 (14.0)

137 (14.7)

16 (9.8)

 Negative

776 (70.9)

658 (70.8)

118 (71.9)

 Unknown^a

165 (15.1)

135 (14.5)

30 (18.3)

Subtype

 HR + HER2-

584 (53.4)

499 (53.7)

85 (51.8)

 HR + HER2+

76 (6.9)

68 (7.3)

8 (4.9)

 HR-HER2+

77 (7.0)

69 (7.4)

8 (4.9)

 HR-HER2-

188 (17.2)

155 (16.7)

33 (20.1)

 Unknown^a

169 (15.4)

139 (14.9)

30 (18.3)

Ki-67 level

 Low (≤ 20%)

466 (42.6)

400 (43.0)

66 (40.2)

 High (>  20%)

467 (42.7)

396 (42.6)

71 (43.3)

 Unknown^a

161 (14.7)

134 (14.4)

27 (16.5)

Grade

 I-II

337 (30.8)

292 (31.4)

45 (27.4)

 III

373 (34.1)

318 (34.2)

55 (33.5)

 Unknown^a

384 (35.1)

320 (34.4)

64 (39.0)