Table 3

Percentage of estrogen receptor (ER)-positive breast cancers by age at diagnosis

ClassClass descriptionN (%)ER+%Pa
1Noncarriers
 Age <45 yrs59 (24.7)61.2P1/2 = 0.872
 Age 45–55 yrs72 (30.1)59.7P1/3 = 0.018
 Age 55–65 yrs108 (45.2)78.7P2/3 = 0.007
Ptrend = 0.008
2 BRCA1
 Age <45 yrs142 (68.3)19.0P1/2 = 0.095
 Age 45–55 yrs45 (21.6)31.1P1/3 = 0.054
 Age 55–65 yrs21 (10.1)38.0P2/3 = 0.562
Ptrend = 0.020
3 BRCA2
 Age <45 yrs43 (48.8)83.7P1/2 = 0.196
 Age 45–55 yrs35 (39.8)71.4P1/3 = 0.799
 Age 55–65 yrs10 (11.4)80.0P2/3 = 0.566
Ptrend = 0.418
4Untested
 Age <45 yrs177 (29.7)65.5P1/2 = 0.061
 Age 45–55 yrs240 (40.3)73.6P1/3 = 0.003
 Age 55–65 yrs179 (30.0)79.3P2/3 = 0.202
Ptrend = 0.003
  • a Pa/b represents the P for the t test between ER+% in classes a and b, therefore P1/2 for noncarriers is the P value for the t test comparing ER+% in those diagnosed <45 years (class 1) and those diagnosed 45–55 years (class 2). Ptrend represents the P calculated from the two-sided Cochran-Armitage trend test.