Breast cancer risk factors in relation to molecular subtypes in breast cancer patients from Kenya

Sayed, Shahin; Fan, Shaoqi; Moloo, Zahir; Wasike, Ronald; Bird, Peter; Saleh, Mansoor; Shaikh, Asim Jamal; Figueroa, Jonine D.; Naidoo, Richard; Makokha, Francis W.; Gardner, Kevin; Oigara, Raymond; Njoroge, Faith Wambui; Magangane, Pumza; Mutebi, Miriam; Chauhan, Rajendra; Mwanzi, Sitna; Govender, Dhirendra; Yang, Xiaohong R.

doi:10.1186/s13058-021-01446-3

Breast Cancer Research

Table 3. Associations between breast cancer risk factors and ER status in Kenyan breast cancer patients (N=838)

From: Breast cancer risk factors in relation to molecular subtypes in breast cancer patients from Kenya

	ER⁺ N=582		ER^- N=256		ER^- vs. ER+
	N	%	N	%	OR (95% CI)†	P†
Age at diagnosis/year
20–39	155	26.8	54	21.1	1.00 (Ref)
40–49	166	28.7	76	29.7	1.38 (0.82, 2.32)	0.23
50–59	138	23.9	73	28.5	1.20 (0.51, 2.83)	0.68
≥ 60	119	20.6	53	20.7	0.84 (0.30, 2.35)	0.74
Trend‡					0.995 (0.72, 1.39)	0.98
BMI/ kg/m²
Normal (< 25.0)	136	29.8	74	34.6	1.00 (Ref)
Overweight (25.0–29.9)	185	40.5	79	36.9	0.77 (0.49, 1.21)	0.26
Obese (≥ 30.0)	136	29.8	61	28.5	0.84 (0.51, 1.38)	0.49
Trend‡					0.92 (0.71, 1.18)	0.49
Premenopausal: BMI^a
Normal (< 25.0)	89	34.6	41	39.8	1.00 (Ref)
Overweight (25.0–29.9)	102	39.7	30	29.1	0.58 (0.31, 1.10)	0.09
Obese (≥ 30.0)	66	25.7	32	31.1	0.91 (0.46, 1.77)	0.77
Trend‡					0.93 (0.66, 1.31)	0.69
Postmenopausal: BMI^a
Normal (< 25.0)	47	23.6	33	29.7	1.00 (Ref)
Overweight (25.0–29.9)	83	41.7	49	44.1	1.07 (0.55, 2.08)	0.85
Obese (≥ 30.0)	69	34.7	29	26.1	0.77 (0.37, 1.61)	0.49
Trend‡					0.87 (0.61, 1.26)	0.47
Age at menarche/year
≤ 13 (9–13)	141	25.4	57	23.2	1.00 (Ref)
14	139	25.0	71	28.9	1.57 (0.94, 2.61)	0.083
≥ 15 (15–20)	276	49.6	118	48.0	1.29 (0.81, 2.04)	0.28
Trend‡					1.10 (0.88, 1.37)	0.41
Age at first pregnancy/year
< 20	130	22.9	86	34.1	1.00 (Ref)
20–24	253	44.5	108	42.9	0.71 (0.44, 1.15)	0.16
25–29	115	20.2	35	13.9	0.58 (0.30, 1.11)	0.10
Nulliparous^b or age ≥30	70	12.3	23	9.1	1.14 (0.48, 2.70)	0.76
Trend‡					0.92 (0.71, 1.20)	0.54
Parity
Nulliparous^b	37	6.4	7	2.7	0.36 (0.10, 1.32)	0.12
Parous	545	93.6	249	97.3	1.00 (Ref)
Number of children
1–2	171	31.4	55	22.1	1.00 (Ref)
3–4	217	39.8	90	36.1	1.43 (0.86, 2.36)	0.16
≥ 5	157	28.8	104	41.8	2.03 (1.11, 3.72)	0.021
Trend‡					1.43 (1.05, 1.93)	0.021
Cumulative breastfeeding duration/month^c
Q1: 1–< 39	152	28.8	39	16.2	1.00 (Ref)
Q2: 39–< 62	127	24.1	65	27.0	2.38 (1.33, 4.24)	0.0033
Q3: 62–< 96	124	23.5	58	24.1	1.44 (0.74, 2.80)	0.28
Q4: ≥ 96	124	23.5	79	32.8	1.58 (0.76, 3.30)	0.22
Trend‡					1.10 (0.87, 1.39)	0.43
Mean breastfeeding duration per child/month
< 12	84	15.9	36	14.9	1.00 (Ref)
12–23	277	52.6	130	53.9	1.10 (0.62, 1.94)	0.74
≥ 24	166	31.5	75	31.1	1.25 (0.68, 2.30)	0.48
Trend‡					1.12 (0.83, 1.51)	0.45
Age at first pregnancy and number of children
Age 25+ years, 1–3 births	117	22.0	37	15.0	1.00 (Ref)
Age < 25 years, 1–3 births	173	32.6	71	28.9	1.20 (0.68, 2.12)	0.53
Age 25+ years, 4+ births	34	6.4	15	6.1	1.47 (0.60, 3.61)	0.40
Age < 25 years, 4+ births	207	39.0	123	50.0	1.69 (0.93, 3.05)	0.085
Trend‡					1.19 (0.99, 1.43)	0.063
Number of children and cumulative breastfeeding duration
Nulliparous or ≤ 3 children and < 62 months	265	47.0	89	35.9	1.00 (Ref)
≤ 3 children and ≥ 62 months	56	9.9	23	9.3	1.09 (0.56, 2.09)	0.81
≥ 4 children and < 62 months	51	9.0	22	8.9	1.52 (0.74, 3.09)	0.25
≥ 4 children and ≥ 62 months	192	34.0	114	46.0	1.44 (0.89, 2.34)	0.14
Trend‡					1.14 (0.97, 1.33)	0.12
Menopausal status^a
Premenopausal	317	54.6	121	47.5	1.00 (Ref)
Postmenopausal	264	45.4	134	52.5	1.44 (0.74, 2.81)	0.28
Age at menopause/year^d
< 50	117	21.8	74	31.5	1.00 (Ref)
> 50	102	19.0	40	17.0	0.73 (0.40, 1.36)	0.32

† Point estimates and 95% confidence intervals were from multivariable models, adjusting for the same series of covariates (except where noticed): age at diagnosis, BMI, age at menarche, age at first pregnancy, number of children, mean breastfeeding duration per child, age at menopause, family history of breast cancer in first-degree female relative, occupation, education level, and location of facility. Estimates of numbers of children, cumulative and averaged breastfeeding duration, and combined age at first pregnancy and number of children were computed among parous women. ‡ Results were from the trend analysis using the categorical risk factor as a trend. ^aMultivariable modeling analysis without adjusting for age at menopause. ^bWomen who reported never pregnant, never gave birth, and had no child were grouped as “Nulliparous” in modeling analyses. ^c Multivariable modeling analysis without adjusting for mean breastfeeding duration per child. ^d Multivariable Modeling analysis was restricted to postmenopausal women. BMI, body mass index; CI, confidence interval; ER, estrogen receptor; OR, odds ratio; Q, quartile

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