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Table 2 Study population and tumor characteristics by ER status in the NHS and the NHSII

From: Alcohol consumption and breast tumor gene expression

  ER+ tumors
N = 471
ER- tumors
N = 127
  Mean SD Mean SD
Age at diagnosis, years 61.4 9.6 59.1 8.9
BMI at diagnosis, kg/m2 26.0 5.0 26.1 5.1
Parity 2.6 1.8 2.9 1.8
Recent alcohol, g/day 6.5 11.7 5.8 10.0
Cumulative average alcohol, g/day 6.4 9.5 5.5 8.2
  N % N %
First-degree family history 79 16.8 16 12.6
Year of diagnosis
 1990‒1999 251 53.3 91 71.7
 2000 − 2004 182 38.6 26 20.5
 2005‒2009 38 8.1 10 7.9
Tumor size
 0.1‒2.0 cm 365 77.5 68 53.5
 2.1‒4.0 cm 75 15.9 46 36.2
 > 4.0 cm 23 4.9 7 5.5
 Unknown 8 1.7 6 4.7
Lymph node involvement
 None 349 74.1 95 74.8
 1‒3 positive nodes 85 18.0 22 17.3
 > 3 positive nodes 33 7.0 8 6.3
 Metastatic at diagnosis 4 0.8 1 0.8
 Unknown 0 0 1 0.8
Grade
 Well-differentiated 124 26.3 6 4.7
 Moderately differentiated 243 51.6 35 27.6
 Poorly differentiated 89 18.9 67 52.8
 Unknown 15 3.2 19 15.0
Stagea
 I 305 64.8 57 44.9
 II 122 25.9 59 46.5
 III 40 8.5 9 7.1
 IV 4 0.8 1 0.8
 Unknown 0 0 1 0.8
  1. ER estrogen receptor, NHS Nurses’ Health Study, BMI body mass index
  2. aStaging was based on tumor size and lymph node involvement