Table 4.

Polytomous model and the joint Cox model on the AARP data to evaluate current BMI with four subtypes of breast cancer defined by the tumor's ER and PR status

Polytomous modelBMI < 25.0BMI 25.0–29.9Relative OR (CI)BMI ≥ 30.0Relative OR (CI)PtrendP value difference in trend
ER+/PR+
 Cases2863451(ref)3661(ref)
 OR (CI)1 (ref)1.589 (1.333–1.894)a2.100 (1.753–2.516)a<0.0001Ref
ER/PR
 Cases84910.901710.577
 OR (CI)1 (ref)1.424 (1.025–1.979)a(0.617–1.316)1.192 (0.824–1.725)(0.394–0.844)a0.2830.012
ER/PR+
 Cases945
 OR (CI)1(ref)
ER+/PR
 Cases97730.585610.4330.531<0.0001
 OR (CI)1 (ref)0.885 (0.635–1.233)(0.385–0.890)0.902 (0.626–1.299)(0.286–0.654)a
Joint Cox modelRelative HR (CI)Relative HR (CI)Relative HR and CI for trend
ER+/PR+1 (ref)1.551 (1.304–1.845)a1 (ref)1.758 (1.471–2.101)1 (ref)<0.0001Ref
ER/PR0.9250.5930.783
1 (ref)1.434 (1.034–1.990)a(0.639–1.338)1.043 (0.729–1.493)(0.399–0.883)a0.693(0.654–0.938)a
ER/PR+0.3420.4280.631
1 (ref)0.531 (0.139–2.021)(0.089–1.316)0.756 (0.224–2.531)(0.126–1.456)0.599(0.317–1.257)
ER+/PR0.5550.4300.659
1 (ref)0.861 (0.620–1.194)(0.384–0.802)a0.756 (0.532–1.075)(0.291–0.636)a0.113(0.544–0.798)a

NOTE: Model adjusted for age, age at menarche, age at first live birth, parity, smoking, educational level, race, family history of breast cancer, fat intake, alcohol consumption, oophorectomy, physical activity, and height (in polytomous model, all the adjusting variables have different coefficients across subtypes; in the joint Cox model, those adjusting variables with the similar coefficient across subtypes are set to have the same coefficient).