Table 4 Prognostic indicators for breast cancers diagnosed in ever- vs never screeneda women, New Zealand women aged 45–69 years at year of diagnosis, 2000–2011

From: Mammography service screening and breast cancer mortality in New Zealand: a National Cohort Study 1999–2011

  Ever screened Never screened  
Prognostic indicator n % n % Significance of difference
Grade of tumour      
 Well differentiated 3725 29.6 1624 18 χ2(1)=384, P<0.0001
Excluding not recorded or NA (n=1498)   31.2   19.9 χ2(1)=321, P<0.0001
 Moderately differentiated 5196 41.3 3679 40.3  
 Poorly or undifferentiated or anaplastic 3014 24 2877 31.8  
 Not recorded/NA 638 5.1 860 9.5  
  Overall heterogeneity: χ2(3)=558, P<0.0001  
Extent of disease      
 Localised 7928 63.1 4169 46.1 χ2(1)=613, P<0.0001
Excluding unknown (n=1697)   67.3   51.2 χ2(1)=521, P<0.0001
 Adjacent organ or regional lymph node 3662 29.1 3521 38.9  
 Distant 190 1.5 447 4.9  
Distant÷(distant+regional)   4.9   11.3 RR=0.44 (0.37–0.52)
 Unknown 793 6.3 904 10 χ2(1)=105, P<0.0001
  Overall heterogeneity: χ2(3)=724, P<0.0001  
Multiple tumours      
 No 12 344 98.2 8697 96.2 RR=0.48 (0.41–0.56)
 Yes 229 1.8 344 3.8 χ2(1)=80.2, P<0.0001
Maximum tumour size mm   mm   
 Mean 18.1   24.4   t=−25.8, P<0.0001
 Median 15   20   z=−27.8, P<0.0001b
  1. Abbreviation: NA=not available.
  2. aAs screened by Breastscreen Aotearoa.
  3. bTwo-sample median test.