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Table 6.

Exogenous hormone use and breast cancer risk stratified by hormone receptor expression

First author (reference)Country (study)Cases (n)Risk estimate (95% CI)*
Combination oral contraceptives     
   ER+ ER− 
    Althuis (28) United States (WISH) 1,375 1.6 (0.9-2.8) 3.1 (1.6-5.9) 
    Stanford (38) United States (CASH-GA) 458 0.8 (0.6-1.2) 1.2 (0.8-1.8) 
    McTiernan (39) United States (CASH-WA) 240 1.2 (0.7-1.9) 0.8 (0.5-1.4) 
    Cooper (36) Australia 380 0.9 (0.5-1.5) 1.3 (0.7-2.6) 
   ER+/PR+ ER−/PR− 
    Cotterchio (24) Canada (ON) 3,276 0.9 (0.6-1.2) 1.2 (0.8-1.9) 
    McCredie (23) Melbourne (Australia) 618 1.1 (0.7-1.9) 0.9 (0.5-1.6) 
    Britton (29) United States (WISH) 1,212 1.2 (0.9-1.5) 1.5 (1.0-2.1) 
    Huang (32) United States (CBCS) 783 1.5 (0.8-2.7) 1.1 (0.6-1.9) 
Hormone Replacement Therapy     
   ER+ ER− 
    Chlebowski (13) WHI 309 1.4 (1.1-1.7)CHRT 1.5 (0.8-2.9)CHRT 
    Cooper (36) Australia 380 0.9 (0.5-1.4)NS 1.8 (0.5-2.2)NS 
    Hildreth (42) United States (CT) 148 0.9 (0.7-1.2)NS 1.3 (0.9-1.8)NS 
    Stanford (38) United States (CASH-GA) 458 1.0 (0.7-1.4)NS 1.0 (0.7-1.3)NS 
   PR+ PR− 
    Chlebowski (13) WHI 309 1.5 (1.1-2.0)CHRT 1.2 (0.8-1.8)CHRT 
   ER+/PR+ ER−/PR− 
    Li (25) Western WA 900 1.1 (0.8-1.5)ERT 1.0 (0.6-1.7)ERT 
   2.0 (1.5-2.7)CHRT 0.9 (0.5-1.8)CHRT 
    Huang (32) United States (CBCS) 783 0.9 (0.6-1.2)NS 0.6 (0.4-0.9)NS 
    Potter (17) IWHS 610 1.1 (0.9-1.3)NS 1.1 (0.7-1.8)NS 
DES exposure in utero     
   ER+ ER− 
    Palmer (14) United States (DES) 41 1.9 (0.8-4.5) 0.4 (0.1-1.9) 
First author (reference)Country (study)Cases (n)Risk estimate (95% CI)*
Combination oral contraceptives     
   ER+ ER− 
    Althuis (28) United States (WISH) 1,375 1.6 (0.9-2.8) 3.1 (1.6-5.9) 
    Stanford (38) United States (CASH-GA) 458 0.8 (0.6-1.2) 1.2 (0.8-1.8) 
    McTiernan (39) United States (CASH-WA) 240 1.2 (0.7-1.9) 0.8 (0.5-1.4) 
    Cooper (36) Australia 380 0.9 (0.5-1.5) 1.3 (0.7-2.6) 
   ER+/PR+ ER−/PR− 
    Cotterchio (24) Canada (ON) 3,276 0.9 (0.6-1.2) 1.2 (0.8-1.9) 
    McCredie (23) Melbourne (Australia) 618 1.1 (0.7-1.9) 0.9 (0.5-1.6) 
    Britton (29) United States (WISH) 1,212 1.2 (0.9-1.5) 1.5 (1.0-2.1) 
    Huang (32) United States (CBCS) 783 1.5 (0.8-2.7) 1.1 (0.6-1.9) 
Hormone Replacement Therapy     
   ER+ ER− 
    Chlebowski (13) WHI 309 1.4 (1.1-1.7)CHRT 1.5 (0.8-2.9)CHRT 
    Cooper (36) Australia 380 0.9 (0.5-1.4)NS 1.8 (0.5-2.2)NS 
    Hildreth (42) United States (CT) 148 0.9 (0.7-1.2)NS 1.3 (0.9-1.8)NS 
    Stanford (38) United States (CASH-GA) 458 1.0 (0.7-1.4)NS 1.0 (0.7-1.3)NS 
   PR+ PR− 
    Chlebowski (13) WHI 309 1.5 (1.1-2.0)CHRT 1.2 (0.8-1.8)CHRT 
   ER+/PR+ ER−/PR− 
    Li (25) Western WA 900 1.1 (0.8-1.5)ERT 1.0 (0.6-1.7)ERT 
   2.0 (1.5-2.7)CHRT 0.9 (0.5-1.8)CHRT 
    Huang (32) United States (CBCS) 783 0.9 (0.6-1.2)NS 0.6 (0.4-0.9)NS 
    Potter (17) IWHS 610 1.1 (0.9-1.3)NS 1.1 (0.7-1.8)NS 
DES exposure in utero     
   ER+ ER− 
    Palmer (14) United States (DES) 41 1.9 (0.8-4.5) 0.4 (0.1-1.9) 

NOTE: Table excludes Morabia et al. (33), who found that risk associated with oral contraceptive use was similarly elevated for ER+ and ER− breast cancers; however, ORs were not presented in the article.

*

Ever-users compared with never-users. ERT, estrogen replacement therapy. CHRT, combination hormone replacement therapy; NS, formulation not specified. ORs were the reported risk estimates for case-control studies and RRs for cohort designs.

Among women ages 20-34 years. No significant association was found among women ages 35-54 years: ER+, OR, 1.0 (0.8-1.3); ER−, OR, 1.2 (0.9-1.6).

HRT modeled as a continuous variable; risk was estimated for every 50 mg/mo of use.

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