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Table 3 Incidence rates, incidence rate differences (IRD) and incidence rate ratios (IRR) of proliferation markers Ki-67 and mitotic count according to age at diagnosis and year of birth

From: Long term trends of breast cancer incidence according to proliferation status

 

Observed

Imputeda

Incidence rate

(cases/100000 person-years)

Incidence rate

(cases/100000 person-years)

 

Age

Women born before 1929

Women born in 1929 or later

IRD

IRR

(95% CI)

Women born before 1929

Women born in 1929 or later

IRD

IRR

(95% CI)

Totalb

40–49

78.3

127.4

49.1

1.6

(1.3–2.1)

     

50–59

110.0

214.4

104.4

1.9

(1.6–2.3)

     

60–69

170.6

298.5

127.9

1.7

(1.5–2.0)

     

70–79

246.5

240.6

−5.9

1.0

(0.8–1.2)

     

Ki-67/500 tumour

cells (%)

< 15

40–49

16.9

34.6

17.7

2.1

(1.2–3.4)

31.9

50.2

18.3

1.6

(1.0–2.5)

50–59

21.8

90.1

68.3

4.1

(2.9–5.9)

49.8

124.2

74.4

2.5

(1.9–3.3)

60–69

58.9

146.3

87.4

2.5

(2.0–3.1)

92.3

186.7

94.4

2.0

(1.6–2.5)

70–79

112.5

121.7

9.2

1.1

(0.8–1.5)

151.2

147.2

−4

1.0

(0.7–1.3)

≥15

40–49

15.9

51.5

35.6

3.2

(1.9–5.4)

46.1

77.1

31.0

1.7

(1.2–2.4)

50–59

31.0

62.3

31.3

2.0

(1.5–2.8)

60.1

90.2

30.1

1.5

(1.1–2.0)

60–69

46.9

83.8

36.9

1.8

(1.4–2.4)

78.1

111.6

33.5

1.4

(1.1–1.8)

70–79

67.2

73.6

6.4

1.1

(0.7–1.7)

94.6

93.0

−1.6

1.0

(0.7–1.4)

Mitotic count (mitoses/mm2)

≤3.6

40–49

17.8

45.4

27.6

2.5

(1.5–4.2)

31.6

66.5

34.9

2.1

(1.4–3.2)

50–59

20.0

101.1

81.1

5.0

(3.5–7.3)

43.2

140.6

97.4

3.3

(3.4–4.4)

60–69

60.9

163.4

102.5

2.7

(2.1–3.4)

90.5

211.9

121.4

2.3

(1.9–2.9)

70–79

110.0

138.7

28.7

1.2

(0.9–1.6)

145.3

166.6

21.3

1.1

(0.9–1.5)

> 3.6

40–49

14.9

40.3

25.4

2.7

(1.6–4.6)

46.4

60.9

14.5

1.3

(0.9–1.9)

50–59

34.6

51.4

16.8

1.5

(1.1–2.0)

66.5

73.8

7.3

1.1

(0.8–1.5)

60–69

48.8

65.9

17.1

1.3

(1.0–1.8)

80.0

86.4

6.4

1.1

(0.8–1.4)

70–79

73.8

59.4

−14.4

0.8

(0.5–1.3)

101.1

73.7

−27.4

0.7

(0.5–1.1)

< 7.7

40–49

26.8

66.4

39.6

2.5

(1.7–3.7)

53.6

98.6

45

1.8

(1.3–2.5)

50–59

38.3

132.0

93.7

3.5

(2.6–4.5)

78.8

185.4

106.6

2.4

(1.9–2.9)

60–69

90.4

198.4

108

2.2

(1.8–2.6)

136.6

258.3

121.7

1.9

(1.6–2.2)

70–79

160.0

181.2

21.2

1.1

(0.9–1.5)

203.5

216.6

13.1

1.1

(0.8–1.3)

≥7.7

40–49

5.9

19.3

13.4

3.2

(1.4–7.5)

24.3

28.8

4.05

1.2

(0.7–2.1)

50–59

16.4

20.5

4.1

1.2

(0.8–2.0)

30.9

28.9

−2

0.9

(0.6–1.5)

60–69

19.3

30.8

11.5

1.6

(1.0–2.5)

33.8

40.0

6.2

1.2

(0.8–1.9)

70–79

29.9

17.0

−12.9

0.6

(0.2–1.3)

43.0

23.7

−19.3

0.6

(0.3–1.2)

  1. a Based on 50 imputed datasets using age (5-year categories) and calendar year of diagnosis (continuous), stage (I, II, III, IV, unknown) and extent of disease (disease localized to the breast, local invasion, regional lymph nodes, distant lymph nodes or organ metastases, unknown) as reported by the Cancer Registry of Norway, year of birth (5-year categories), observation time after diagnosis (log-transformed) and survival status (alive, death from breast cancer, death from other causes)
  2. b Breast cancer incidence from the Cancer Registry of Norway, including cases with unknown Ki-67-status and mitotic count
  3. Abbreviations: IRD incidence rate difference, IRR incidence rate ratio, CI confidence interval