Table 5.

Tumor characteristics and hazard ratios (HR) and 95% confidence intervals (CI) of death and breast cancer-specific death by self-reported ABO blood type for 2,036 invasive breast cancer cases in the Nurses’ Health Study

	ABO blood type
	O	A	AB	B
Tumor characteristics (%)
Stage I	66	63	62	65
Stage II	29	33	32	29
Stage III	5	4	6	6
ER positive	84	81	82	89
PR positive	71	68	67	73
Treated with radiation	65	64	65	69
Treated with chemotherapy	38	42	37	37
Treated with tamoxifen or aromatase inhibitor	75	76	77	82
All deaths
N	104	97	30	28
HR (95% CI)*	1.00 (referent)	1.00 (0.74, 1.34)	1.35 (0.87, 2.08)	0.81 (0.52, 1.25)
Death due to breast cancer
N	38	42	15	12
HR (95% CI)*	1.00 (referent)	1.18 (0.72, 1.94)	1.64 (0.83, 3.24)	1.05 (0.52, 2.12)

^*Adjusted for age at diagnosis (continuous), date of diagnosis (continuous), time since diagnosis (stratified), disease stage (I, II, III), radiation treatment (no/yes/missing), chemotherapy and/or hormonal therapy (neither, chemotherapy only, hormonal only, both, missing), ER/PR status (negative/positive), smoking status at diagnosis (never/past/current), BMI at diagnosis (<21, 21–<23, 23–<25, 25–<30, ≥30 kg/m²), menopausal status and postmenopausal hormone use at diagnosis (premenopausal/dubious menopausal status, postmenopausal never user, postmenopausal past user, postmenopausal current user, missing), age at first birth and parity (nulliparous, <25 years and 1–2 births, <25 years and ≥3 births, ≥25 years and 1–2 births, ≥25 years and ≥3 births), oral contraceptive use (never/ever), physical activity after diagnosis and treatment (<2.5, 2.5–<5, 5–<10, 10–<20, 20–<30, ≥30 MET-hours/week), family history of breast cancer (no/yes)