The influence of metabolic factors and ethnicity on breast cancer risk, treatment and survival: The Oslo ethnic breast cancer study

Figures & data

Table 1. Characteristics^a of all participating women according to birth origin: the Oslo Ethnic Breast Cancer Study.

			Ethnic minority women
	Total (n = 13,802)^b	Western European women^a (n = 11,012)^b	All ethnic minority women (n = 2790)^b	South Asian women (n = 1097)^b	Middle Eastern and north African women (n = 724)^b	All other non-western origin women (n = 969)^b
	Mean (SD)	Mean (SD)	Mean (SD)	Mean (SD)	Mean (SD)	Mean (SD)
Characteristics at study entry
Age at attendance (years)	46.7 (14.8)	48.6 (15.4)	39.2 (9.92)	37.9 (9.12)	38.1 (9.25)	41.3 (10.8)
Follow-up (years)	16.5 (3.54)	16.5 (3.73)	16.7 (2.29)	16.7 (2.11)	16.7 (1.66)	16.7 (2.71)
Higher education^c (%)	45.6	48.8	31.5	26.6	29.7	37.1
Income-generating work^d (%)	78.4	84.7	56.5	51.8	48.6	67.7
Reproductive factors
Number of children	1.58 (1.33)	1.41 (1.18)	2.23 (1.64)	2.40 (1.57)	2.29 (1.66)	2.00 (1.66)
Age at menarche (years)	13.4 (1.68)	13.3 (1.49)	13.7 (2.27)	13.8 (2.66)	13.3 (1.95)	13.9 (1.89)
Clinical variables
Height (cm)	164 (7.51)	166 (6.51)	157 (6.80)	156 (5.76)	158 (7.50)	157 (7.09)
BMI (kg/m^2)	25.4 (4.55)	25.1 (4.40)	26.5 (5.01)	27.2 (4.91)	27.8 (5.43)	24.6 (4.56)
Waist:hip ratio	0.80 (0.07)	0.79 (0.07)	0.82 (0.08)	0.84 (0.08)	0.81 (0.07)	0.80 (0.07)
Systolic blood pressure (mHg)	126 (19.4)	128 (19.7)	118 (15.8)	118 (15.5)	116 (14.3)	120 (17.0)
Diastolic blood pressure (mmHg)	71.7 (11.2)	72.5 (11.2)	68.9 (10.5)	69.0 (10.3)	66.9 (9.77)	70.1 (11.2)
Serum samples
T cholesterol (mmol/l)	5.48 (1.12)	5.60 (1.12)	5.02 (0.99)	4.94 (0.92)	4.91 (0.99)	5.17 (1.04)
HDL-C (mmol/l)	1.59 (0.42)	1.65 (0.41)	1.37 (0.35)	1.24 (0.29)	1.36 (0.32)	1.53 (0.38)
TGs (mmol/l)	1.39 (0.93)	1.31 (0.83)	1.60 (1.16)	1.84 (1.36)	1.51 (1.04)	1.41 (0.95)
TG:HDL-C	0.99 (0.98)	0.90 (0.81)	1.35 (1.41)	1.67 (1.80)	1.24 (1.09)	1.06 (0.96)
Lifestyle factors/Comorbidity (%)
MHT users^e	16.8	19.8	6.75	5.58	9.30	6.20
Blood pressure treatment^f	9.85	10.6	6.89	7.77	6.06	6.38
C-lowering treatment^g	5.05	5.29	4.03	5.37	4.37	2.27
Diabetes mellitus	2.70	1.96	5.93	9.30	4.50	3.20
Alcohol consumption^h	56.8	67.1	13.2	3.60	10.5	25.3
Current cigarette smokers	25.2	28.5	11.4	1.40	23.2	13.2
Moderate physical activity^i	51.9	57.3	29.8	28.5	27.7	33.7

BMI: body mass index (kg/m²); C: cholesterol; HDL: high-density lipoprotein; MHT: menopausal hormone therapy; n: number of participants; SD: standard deviation; T: total; TG: triglyceride.

^aWestern European women: women born in Norway with Norwegian ancestry and western immigrants; Nordic countries, western Europe, Australia and North America.

^bNumbers may vary due to missing information.

^cCollege and/or university education, ≥14 years of school.

^dCurrent full- or part-time work.

^ePrevious or current MHT use.

^fCurrent blood pressure treatment.

^gCurrent cholesterol-lowering treatment.

^hAlcohol consumption defined by times per month.

ⁱModerate physical activity defined by ≥3 h of light activity and/or ≥1 h heavy exercise per week.

Table 2. Breast tumor characteristics and treatment modalities for western European and ethnic minority breast cancer cases: the Oslo Ethnic Breast Cancer Study.

	Western European^a breast cancer cases (ncases= 487)^b	Ethnic minority breast cancer cases (ncases = 70)^b
	Mean (SD)	Mean (SD)
Age at diagnosis (years)	61.6 (12.7)	53.8 (8.43)
Follow- up after diagnosis (years)	7.85 (5.31)	7.11 (6.10)
Tumor characteristics
Histological subtype (%)
Invasive carcinoma NST	78.3	92.2
Invasive lobular carcinoma	12.7	3.10
Others	9.00	4.70
Tumor size (mm)	22.4 (19.0)	24.3 (20.1)
Lymph node positive (%)	35.1	29.9
Disease stage (%)
1–2	84.5	80.6
3	12.6	17.9
4	2.90	1.50
Histological grading (%)
1	25.6	21.9
2	48.8	34.4
3	25.6	43.8
ER positive (%)	85.6	73.9
PgR positive (%)	65.8	58.5
HER2 positive (%)	12.8	22.6
Ki-67 %	29.8 (21.6)	33.0 (19.2)
Treatment (%)
Mastectomy	35.7	37.9
Breast-conserving treatment	57.0	59.1
Other type of surgery	3.50	3.00
SN dissection	64.7	65.1
Axillary dissection	32.1	34.9
Treatment intention
Curative	94.9	98.5
Palliative	5.10	1.50
Chemotherapy	41.1	65.2
Anthracyclines^c	38.8	63.6
Taxanes^d	20.0	36.4
Endocrine therapy	57.9	55.4
Tamoxifen	30.7	30.7
Aromatase inhibitors	35.4	24.6
Trastuzumab	9.35	14.7
Radiotherapy	73.0	87.5
Local radiation	64.2	60.7
Locoregional radiation	35.8	39.3

^aWestern European women: women born in Norway with Norwegian ancestry and western immigrants; Nordic countries, western Europe, Australia and North America.

^bNumbers may vary due to missing information.

^cFEC-60, FEC-100 or EC-90.

^dPaclitaxel or docetaxel.

EC: epirubicin; cyclophosphamide; ER: estrogen receptor; FEC: 5-fluorouracil, epirubicin, cyclophosphamide; HER2; human epidermal growth factor receptor-2; NST: no special type; PgR: progesterone receptor; SN: sentinel node.

Table 3. Multivariable-adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for breast cancer risk comparing all (n = 2,790) ethnic minority women with western European women (n = 11,012), and south Asian women (n = 1097) with western European women, by metabolic factors and metabolic profiles: the Oslo Ethnic Breast Cancer Study.

		Western European women^a(n = 11,012)		Ethnic minority women^b (n = 2,790)
	ncases	HR (95% CI)	ncases	HR (95% CI)
Metabolic factors
BMI
≤24.6 kg/m^2	245	1.00 (ref)	18	0.34 (0.27–0.74)
>24.6 kg/m^2	242	1.00 (ref)	52	1.16 (0.82–1.62)
WHR
≤0.79	273	1.00 (ref)	29	0.75 (0.50–1.10)
>0.79	214	1.00 (ref)	41	0.88 (0.61–1.29)
TG:HDL-C
≤0.73	268	1.00 (ref)	22	0.67 (0.43–1.06)
>0.73	219	1.00 (ref)	48	0.90 (0.64–1.29)
BP^c
≤96.5 mmHg	212	1.00 (ref)	38	0.66 (0.46–0.95)
>96.5 mmHg	275	1.00 (ref)	32	1.03 (0.70–1.53)
Metabolic profile^d
Cat. 1:0–2 factors	311	1.00 (ref)	35	0.66 (0.46–0.95)
Cat. 2: 3 factors	93	1.00 (ref)	17	0.88 (0.48–1.62)
Cat. 3: 4 factors	83	1.00 (ref)	18	1.53 (0.86–2.71)
		Western European women^a(n = 11,012)		South Asian women (n = 1,097)
	ncases	HR (95% CI)	ncases	HR (95% CI)
Metabolic factors
BMI
≤24.6 kg/m^2	245	1.00 (ref)	6	0.51 (0.22–1.17)
>24.6 kg/m^2	242	1.00 (ref)	25	1.29 (0.82–2.03)
WHR
≤0.79	273	1.00 (ref)	6	0.63 (0.28–1.44)
>0.79	214	1.00 (ref)	25	1.13 (0.71–1.79)
TG:HDL-C
≤0.73	268	1.00 (ref)	3	0.38 (0.12–1.19)
>0.73	219	1.00 (ref)	28	1.16 (0.75–1.80)
BP^c
≤96.5 mmHg	212	1.00 (ref)	13	0.62 (0.35–1.14)
>96.5 mmHg	275	1.00 (ref)	18	1.47 (0.90–2.46)
Metabolic profile^d
Cat. 1: 0–2 factors	311	1.00 (ref)	9	0.60 (0.30–1.18)
Cat. 2: 3 factors	93	1.00 (ref)	9	0.93 (0.43–2.00)
Cat. 3: 4 factors	83	1.00 (ref)	13	2.30 (1.18–4.49)

Cox’s proportional hazard regression.

^aWestern European women: women born in Norway with Norwegian ancestry and western immigrants; Nordic countries, western Europe, Australia and North America.

^bSouth Asia, Middle East and north Africa, eastern Europe, East Asia, sub-Saharan Africa, South and Central America.

^cBP = (SBP + DBP)/2.

^dFactors included: Above median levels of BMI (>24.6 kg/m²), WHR (>0.79), TG:HDL-C (>0.73) and BP (>96.5 mmHg).

Adjusted for age, age at menarche, number of children.

BMI: body mass index; BP: blood pressure; Cat.: category; DBP: diastolic blood pressure; HDL-C: high-density lipoprotein-cholesterol; n: number of participants; n_cases: number of cases; ref: reference; SBP: systolic blood pressure; TG: triglycerides; WHR: waist:hip ratio.

Table 4. Age- and multivariable-adjusted odds ratios (ORs) and 95% confidence intervals (CIs) comparing ethnic minority women and western European women by breast cancer subtype and received treatment.

	Western European breast cancer cases^a (ncases = 381)		Ethnic minority breast cancer cases (ncases = 59)
	ncases	OR (95% CI)	ncases	Age-adjusted OR (95% CI)	Multivariable-adjusted^b OR (95% CI)
Breast cancer subtype^c
Hormone receptor-positive BC	294	1.00 (ref)	35	0.69 (0.41–1.15)	0.47 (0.26–0.86)
HER2-positive BC	49	1.00 (ref)	13	1.51 (0.76–3.00)	1.68 (0.81–3.50)
Triple-negative BC	38	1.00 (ref)	11	2.27 (1.07–4.79)	2.11 (0.97–4.61)
Breast cancer treatment^d
Curative treatment intention	361	1.00 (ref)	58	1.29 (0.16–10.6)	1.36 (0.16–11.3)
Mastectomy	136	1.00 (ref)	20	1.12 (0.61–2.02)	0.94 (0.51–1.75)
Breast conservative treatment	213	1.00 (ref)	36	1.01 (0.56–1.82)	1.20 (0.65–2.21)
SN dissection	242	1.00 (ref)	41	1.24 (0.67–2.29)	1.37 (0.73–2.56)
Axillary lymph node dissection	125	1.00 (ref)	17	0.73 (0.39–1.35)	0.64 (0.34–1.21)
Endocrine therapy	228	1.00 (ref)	31	0.79 (0.45–1.41)	1.05 (0.55–2.04)
Tamoxifen	109	1.00 (ref)	16	0.68 (0.36–1.28)	0.77 (0.39–1.52)
Aromatase inhibitor	153	1.00 (ref)	14	0.62 (0.32–1.20)	0.73 (0.37–1.44)
Chemotherapy	179	1.00 (ref)	38	1.22 (0.65–2.29)	0.85 (0.42–1.71)
Anthracyclines	171	1.00 (ref)	37	1.27 (0.68–2.23)	0.94 (0.48–1.83)
Complete anthracyline courses^e	131	1.00 (ref)	29	1.02 (0.43–2.43)	1.02 (0.41–2.52)
Taxanes	90	1.00 (ref)	24	1.65 (0.91–2.99)	1.32 (0.69–2.54)
Complete taxane courses^f	63	1.00 (ref)	15	0.25 (0.08–0.76)	0.26 (0.08–0.82)
Trastuzumab	42	1.00 (ref)	10	1.18 (0.55–2.56)	0.85 (0.37–1.96)
Radiotherapy	280	1.00 (ref)	49	1.28 (0.54–3.04)	1.37 (0.57–3.28)
Local radiotherapy	168	1.00 (ref)	32	1.42 (0.74–2.72)	1.60 (0.82–3.13)
Locoregional radiotherapy	110	1.00 (ref)	17	0.70 (0.37–1.35)	0.62 (0.32–1.22)

Logistic regression analysis.

^aWestern European women: women born in Norway with Norwegian ancestry and western immigrants; Nordic countries, western Europe, Australia and North America.

^bBreast cancer subtype is adjusted for age at diagnosis, year of diagnosis and body mass index (kg/m²). Breast cancer treatment is adjusted for age at diagnosis, year of diagnosis, body mass index (kg/m²) and breast cancer subtype.

^cHormone receptor-positive BC: ER positive (with or without PgR positive) and HER2 negative; HER2-positive BC: all patients with HER2 overexpression; triple-negative BC: ER-, PgR- and HER2 negative.

^dAdjuvant breast cancer treatment.

^eSix courses of FEC-60, four to six courses of FEC-100, or four courses of EC-90.

^fEither 12 courses of weekly paclitaxel or 4 courses of docetaxel.

BC: breast cancer; EC: epirubicin, cyclophosphamide; ER: estrogen receptor; FEC: 5-fluorouracil, epirubicin, cyclophosphamide; HER2: human epidermal growth factor receptor-2; n_cases: number of cases; PgR: Progesterone; ref: reference; SN: sentinel node.

Table 5. Multivariable-adjusted hazard ratios (HRs) for overall mortality by metabolic risk factors (median split) and metabolic profiles (categories) among all breast cancer cases and according to breast cancer subtype: the Oslo Ethnic Breast Cancer Study.

		All breast cancer cases (deaths = 95)		Hormone receptor-positive breast cancer^a (deaths = 69)		HER2 positive-breast cancer^b (deaths = 9)		Triple-negative breast cancer^c (deaths = 17)
	ncases	HR (95% CI)	ncases	HR (95% CI)	ncases	HR (95% CI)	ncases	HR (95% CI)
Metabolic factors^d
BMI
≤24.6 kg/m^2	215	1.00 (ref)	153	1.00 (ref)	38	1.00 (ref)	24	1.00 (ref)
>24.6 kg/m^2	225	1.15 (0.75–1.76)	175	1.11 (0.68–1.83)	24	3.39 (0.82–14.0)	26	0.84 (0.31–2.25)
WHR
≤0.79	252	1.00 (ref)	182	1.00 (ref)	47	1.00 (ref)	23	1.00 (ref)
>0.79	188	1.46 (0.90–2.36)	147	1.85 (1.05–2.15)	15	0.56 (0.11–2.95)	26	1.10 (0.34–3.52)
TG:HDL-C
≤0.73	232	1.00	169	1.00 (ref)	37	1.00 (ref)	26	1.00 (ref)
>0.73	208	1.53 (0.98–2.40)	160	1.20 (0.70–2.07)	25	1.71 (0.38–7.70)	23	2.88 (1.02–8.11)
BP^e
≤96.5 mmHg	208	1.00 (ref)	150	1.00 (ref)	39	1.00 (ref)	19	1.00 (ref)
>96.5 mmHg	232	1.35 (0.83–2.22)	179	1.01 (0.57–1.78)	23	1.07 (0.24–4.71)	30	4.77 (1.01–22.6)
Metabolic profiles^f
Cat. 1 :0–2 factors	284	1.00	207	1.00 (ref)	50	1.00 (ref)	27	1.00 (ref)
Cat. 2: 3 factors	76	1.53 (0.91–2.55)	58	1.72 (0.95–3.15)	7	1.56 (0.16–15.0)	11	0.83 (0.25–3.82)
Cat. 3: 4 factors	80	1.50 (0.92–2.44)	64	1.53 (0.87–2.70)	5	0.95 (0.10–9.34)	11	1.80 (0.53–6.11)
P trend		0.078		0.112		0.935		0.449

Cox’s proportional hazard model.

^aHormone receptor-positive BC: ER positive (with or without PgR positive).

^bHER2-positive BC: all patients with HER2 overexpression.

^cTriple-negative BC: ER-, PgR- and HER2 negative.

^dAdjusted for age at diagnosis, BMI (excluding median splits of BMI), smoking habits, and ethnicity.

^eBP = (SBP + DBP)/2.

^fFactors included: above median levels of BMI (>24.6 kg/m²), WHR (>0.79), TG:HDL-C (>0.73) and BP (>96.5 mmHg). Adjusted to age at diagnosis, smoking habits, and ethnicity.

BMI: body mass index; BP: blood pressure; Cat: category; DBP: diastolic blood pressure; ER: estrogen receptor; HER2: human epidermal growth factor receptor-2; HDL: high-density lipoprotein-cholesterol; n: number of cases; PgR: progesterone receptor; ref: reference; SBP: systolic blood pressure; TG: triglycerides; WHR: waist:hip ratio.

Data availability

The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available due to privacy or ethical restrictions.