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Table 2 Parity and breast cancer risk by ER/PR status

From: Reproductive factors and breast cancer risk according to joint estrogen and progesterone receptor status: a meta-analysis of epidemiological studies

Study

Subgroups by MP status

Exposure categories (n)

Highest/lowest exposure category

RR (95% CI)

    

ER+PR+

ER-PR-

Cohort studies

[9]

Post-MP

3

≥3/Nulliparous

0.75 (0.52–1.06)

2.24 (0.69–7.24)

   

Per birth

0.96 (0.89–1.03)

1.09 (0.91–1.30)

[10]

All women

3

4/Nulliparous

0.74 (0.61–0.89)

1.17 (0.80–1.70)

   

Per birth

0.88 (0.79–0.98)

1.13 (0.92–1.41)

Summary RRs for cohort studies

Highest/Nulliparous

0.74 (0.50–1.10)

1.25 (0.84–1.87)

   

Per birth

0.93 (0.80–1.08)

1.11 (0.95–1.29)

Population-based case-control studies

[12]

Young

2

Ever/Nulliparous

0.83 (0.60–1.15)

0.82 (0.55–1.23)

   

Per birth

0.91 (0.77–1.07)

0.91 (0.74–1.11)

[13]

All women

4

≥3/Nulliparous

0.62 (0.43–0.90)

0.77 (0.46–1.27)

   

Per birth

0.90 (0.82–0.97)

0.94 (0.84–1.06)

 

Pre-MP

4

≥3/Nulliparous

0.44 (0.26–0.75)

0.90 (0.46–1.76)

   

Per birth

0.83 (0.73–0.94)

0.97 (0.83–1.14)

 

Post-MP

4

≥3/Nulliparous

0.71 (0.53–0.97)

0.72 (0.46–1.12)

   

Per birth

0.92 (0.86–0.98)

0.93 (0.84–1.03)

[14]

Young

4

≥3/Nulliparous

1.0 (0.5–1.2)

0.8 (0.4–1.3)

   

Per birth

1.00 (0.90–1.11)

0.94 (0.81–1.09)

[7]

All women

4

≥3/Nulliparous

0.63 (0.54–0.73)

1.07 (0.86–1.32)

   

Per birth

0.86 (0.82–0.90)

1.01 (0.95–1.08)

[8]

Young

4

≥3/Nulliparous

0.61 (0.42–0.88)

0.93 (0.60–1.44)

   

Per birth

0.86 (0.78–0.95)

0.95 (0.84, 1.06)

Summary RRs for population-based case-control studies

Highest/Nulliparous

0.67 (0.55–0.82)

0.96 (0.79–1.17)

   

Per birth

0.88 (0.83–0.94)

0.98 (0.92–1.04)

Hospital-based case-control study

[15]

 

Per birth

Per birth

0.96 (0.79–1.17)

1.00 (0.81–1.23)

Summary RRs by MP status

Pre-MP/Young

 

Highest/Nulliparous

0.72 (0.52–0.98)

0.86 (0.63–1.18)

   

Per birth

0.90 (0.82–0.98)

0.95(0.86–1.04)

 

Post-MP

 

Highest/Nulliparous

0.72 (0.44–1.17)

0.86 (0.53–1.42)

   

Per birth

0.93 (0.84–1.03)

0.97 (0.88–1.08)

Summary RRs for all studies

Highest/Nulliparous

0.75 (0.65–0.88)

1.01 (0.87–1.17)

   

Per birth

0.89 (0.84–0.94)

0.99 (0.94–1.05)

P for homogeneity between ER+PR+ and ER-PR- cancer

Highest/Nulliparous

p <0.001

   

Per birth

p <0.001

  1. Test for homogeneity across all studies: P ER+PR+ = 0.52 and P ER-PR- = 0.77 for highest/nulliparous, P ER+PR+ = 0.84 and P ER-PR-= 0.80 per birth. Egger's test for publication bias for all studies: P ER+PR+ = 0.98 and P ER-PR- = 0.87. CI, confidence interval; ER+, estrogen receptor-positive; ER-, estrogen receptor-negative; ER/PR, estrogen and progesterone receptor; MP, menopausal or menopause; PR+, progesterone receptor-positive; PR-, progesterone receptor-negative; RR, relative risk.