Table 1 Characteristics of 4,353 premenopausal breast cancer patients by patterns of endocrine therapy adherence during five years following diagnosis

Total

2,465 (57)

1,587 (36)

301 (6.9)

Age at diagnosis

 < 40

359 (15)

261 (16)

54 (18)

 40–49

1,548 (63)

975 (61)

173 (57)

 50–55

558 (23)

351 (22)

74 (25)

Charlson Comorbidity Index score

 None

2,234 (91)

1,382 (87)

259 (86)

 One or higher

231 (9.4)

205 (13)

42 (14)

Stage at diagnosis^a

 Stage I

549 (22)

465 (29)

106 (35)

 Stage II

1,398 (57)

837 (53)

147 (49)

 Stage III

518 (21)

285 (18)

48 (16)

Positive lymph nodes^a

 None

832 (34)

637 (40)

147 (49)

 One

658 (27)

391 (25)

60 (20)

 Two or more

975 (40)

559 (35)

94 (31)

Histological grade^a

 I

500 (20)

343 (22)

68 (23)

 II

1,289 (52)

819 (52)

163 (54)

 III

524 (21)

310 (20)

56 (19)

 Unknown/not graded

135 (5.5)

101 (6.4)

13 (4.3)

Tumor size^{a, b}

 < 2 cm

1,354 (55)

969 (61)

189 (63)

 > 2-5 cm

1,019 (41)

 < 580

 < 115

 > 5 cm

92 (3.7)

 < 55

 < 5

HER2 status

 HER2 negative

1,517 (62)

1,030 (65)

189 (63)

 HER2 positive

301 (12)

227 (14)

51 (17)

 Unknown/not measured

647 (26)

330 (21)

61 (20)

Treated with chemotherapy

 Yes

2,354 (96)

1,362 (86)

247 (82)

 No

111 (4.5)

225 (14)

54 (18)

Surgery type and radiotherapy

 Mastectomy without radiotherapy

364 (15)

215 (14)

49 (16)

 Mastectomy and radiotherapy

788 (32)

433 (27)

79 (26)

 Lumpectomy

1,313 (53)

939 (59)

173 (57)