Body mass index at age 18 years and recent body mass index in relation to risk of breast cancer overall and ER/PR/HER2-defined subtypes in white women and African-American women: a pooled analysis

Huiyan Ma; Giske Ursin; Xinxin Xu; Eunjung Lee; Kayo Togawa; Kathleen E. Malone; Polly A. Marchbanks; Jill A. McDonald; Michael S. Simon; Suzanne G. Folger; Yani Lu; Jane Sullivan-Halley; Dennis M. Deapen; Michael F. Press; Leslie Bernstein

doi:10.1186/s13058-017-0931-5

Table 2 Adjusted^a odds ratio (OR) and 95% confidence interval (CI) for breast cancer overall and ER/PR/HER2-defined subtypes associated with BMI in premenopausal women and postmenopausal women

From: Body mass index at age 18 years and recent body mass index in relation to risk of breast cancer overall and ER/PR/HER2-defined subtypes in white women and African-American women: a pooled analysis

	Controls	All cases		Triple negative (ER–/PR–/HER2–)		Luminal-like (ER+ and/or PR+)		HER2-enriched (ER–/PR–/HER2+)		Unclassified
	Number	Number	OR (95% CI)	Number	OR (95% CI)	Number	OR (95% CI)	Number	OR (95% CI)	Number	OR (95% CI)
Premenopausal
BMI at age 18 years, kg/m²
< 20.0	588	1187	Referent	160	Referent	656	Referent	71	Referent	300	Referent
20.0–24.9	543	1067	0.99 (0.84–1.16)	144	0.91 (0.69–1.20)	577	0.97 (0.81–1.17)	55	0.82 (0.55–1.22)	291	1.09 (0.88–1.35)
≥ 25.0	126	173	0.72 (0.53–0.96)	25	0.62 (0.36–1.04)	83	0.63 (0.44–0.91)	6	0.36 (0.14–0.92)	59	1.00 (0.68–1.46)
Per 5 kg/m² increase			0.83 (0.73–0.95)		0.68 (0.53–0.87)		0.80 (0.68–0.95)		0.59 (0.40–0.86)		1.00 (0.84–1.19)
P value			0.007		0.002		0.008		0.006		0.98
					P value for homogeneity of slope coefficients across three subtypes = 0.15
Recent BMI, kg/m²
< 25.0	758	1545	Referent	194	Referent	868	Referent	80	Referent	403	Referent
25.0–29.9	299	533	0.90 (0.74–1.08)	80	1.07 (0.78–1.47)	269	0.82 (0.65–1.02)	29	0.99 (0.61–1.60)	155	0.92 (0.71–1.17)
≥ 30.0	200	349	0.85 (0.67–1.08)	55	1.12 (0.75–1.67)	179	0.80 (0.60–1.06)	23	1.34 (0.75–2.38)	92	0.75 (0.54–1.03)
Per 5 kg/m² increase			1.00 (0.92–1.08)		1.14 (1.00–1.31)		0.97 (0.88–1.07)		1.19 (0.98–1.45)		0.94 (0.84–1.05)
P value			0.94		0.06		0.58		0.07		0.26
					P value for homogeneity of slope coefficients across three subtypes = 0.02
Postmenopausal^b
BMI at age 18 years, kg/m²
< 20.0	522	734	Referent	89	Referent	358	Referent	40	Referent	247	Referent
20.0–24.9	518	673	0.92 (0.78–1.10)	83	0.97 (0.69–1.39)	326	0.94 (0.76–1.17)	35	0.88 (0.53–1.44)	229	0.89 (0.70–1.12)
≥ 25.0	89	100	0.79 (0.56–1.11)	14	1.01 (0.52–1.98)	56	0.99 (0.65–1.50)	5	0.76 (0.27–2.14)	25	0.51 (0.31–0.85)
Per 5 kg/m² increase			0.98 (0.85–1.14)		0.98 (0.73–1.32)		1.12 (0.94–1.35)		0.76 (0.48–1.20)		0.86 (0.70–1.05)
P value			0.81		0.89		0.21		0.23		0.14
					P value for homogeneity of slope coefficients across three subtypes = 0.20
Recent BMI, kg/m²
< 25.0	513	747	Referent	83	Referent	390	Referent	36	Referent	238	Referent
25.0–29.9	353	435	0.95 (0.78–1.16)	64	1.11 (0.76–1.63)	193	0.88 (0.69–1.12)	28	1.23 (0.71–2.12)	150	0.93 (0.71–1.21)
≥ 30.0	263	325	1.09 (0.86–1.39)	39	0.95 (0.59–1.55)	157	1.19 (0.89–1.60)	16	1.11 (0.55–2.25)	113	1.03 (0.75–1.41)
Per 5 kg/m² increase			0.97 (0.90–1.06)		0.97 (0.82–1.15)		0.98 (0.89–1.09)		1.06 (0.83–1.34)		0.95 (0.85–1.07)
P value			0.54		0.74		0.74		0.66		0.39
					P value for homogeneity of slope coefficients across three subtypes = 0.83
Postmenopausal/never used MHT
Recent BMI, kg/m²
< 25.0	186	283	Referent	33	Referent	148	Referent	15	Referent	87	Referent
25.0–29.9	150	181	0.94 (0.68–1.29)	27	0.92 (0.50–1.71)	74	0.82 (0.55–1.21)	11	0.98 (0.41–2.34)	69	1.06 (0.70–1.61)
≥ 30.0	130	186	1.39 (0.98–1.99)	20	0.96 (0.50–2.00)	86	1.55 (1.00–2.41)	9	1.20 (0.44–3.30)	71	1.42 (0.90–2.25)
Per 5 kg/m² increase			1.07 (0.95–1.21)		0.99 (0.77–1.27)		1.07 (0.92–1.25)		1.10 (0.77–1.56)		1.10 (0.94–1.28)
P value			0.27		0.94		0.36		0.60		0.26
					P value for homogeneity of slope coefficients across three subtypes = 0.81
Postmenopausal/ever used MHT
Recent BMI, kg/m²
< 25.0	327	464	Referent	50	Referent	242	Referent	21	Referent	151	Referent
25.0–29.9	203	254	0.93 (0.72–1.21)	37	1.12 (0.67–1.87)	119	0.89 (0.65–1.22)	17	1.41 (0.68–2.90)	81	0.86 (0.60–1.22)
≥ 30.0	133	139	0.86 (0.62–1.20)	19	0.87 (0.44–1.69)	71	0.94 (0.63–1.42)	7	0.91 (0.33–2.50)	42	0.75 (0.47–1.19)
Per 5 kg/m² increase			0.90 (0.79–1.01)		0.96 (0.75–1.21)		0.92 (0.79–1.06)		1.01 (0.71–1.42)		0.82 (0.69–0.98)
P value			0.07		0.71		0.24		0.98		0.03
					P value for homogeneity of slope coefficients across three subtypes = 0.85

Abbreviations: ER estrogen receptor, PR progesterone receptor, HER2 human epidermal growth factor receptor-2, BMI body mass index, MHT menopausal hormone therapy
^aORs obtained from multivariable polychotomous unconditional logistic regression models with mutual adjustment of BMI at age 18 years and recent BMI and with adjustment for source study, study site, race, education, reference age, first-degree breast cancer family history, age at menarche, number of completed pregnancies, lifetime recreational physical activity, alcohol intake, cigarette smoking status, and oral contraceptive use
^bModel described (^a) is additionally adjusted for MHT use

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