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 1 Distributions of breast cancer risk factors in Kenyan breast cancer patients, overall and by hospitals (N=838)

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

			Hospitals
	Overall (n=838)		AKU (n=350, 42%)		Kijabe (n=105, 13%)		Nyeri (n=110, 13%)		St Mary’s (n=122, 15%)		Others (n=151, 18%)
	N	%	N	%	N	%	N	%	N	%	N	%	P*
Demographic
Age at diagnosis/year
20–29	32	3.8	17	4.9	2	1.9	2	1.9	5	4.1	6	4.0	0.11
30–39	177	21.2	64	18.3	23	21.9	22	20.4	34	28.1	34	22.5
40–49	242	29.0	100	28.7	37	35.2	34	31.5	35	28.9	36	23.8
50–59	211	25.3	105	30.1	26	24.8	23	21.3	19	15.7	38	25.2
≥ 60	172	20.6	63	18.1	17	16.2	27	25.0	28	23.1	37	24.5
Mean (SD)	49.2 (12.8)	49.0 (11.2)	48.4 (11.3)	50.5 (13.5)	48.7 (15.1)	49.7 (12.9)
Median (IQR)	48 (39, 57)	49 (40, 56)	47 (41, 57)	49 (41, 60)	45 (37, 58)	49 (39, 59)
Missing	4		1		0		2		1		0
BMI/ kg/m²
Normal (< 25.0)	210	31.3	67	21.3	35	40.2	25	39.7	36	40.4	47	40.2	< 0.0001
Overweight (25.0–29.9)	264	39.3	126	40.0	33	37.9	28	44.4	37	41.6	40	34.2
Obese (≥ 30.0)	197	29.4	122	38.7	19	21.8	10	15.9	16	18.0	30	25.6
Missing	167		35		18		47		33		34
Family history of breast cancer in first-degree female relatives
No	773	92.2	314	89.7	100	95.2	99	90.0	119	97.5	141	93.4	0.036
Yes	65	7.8	36	10.3	5	4.8	11	10.0	3	2.5	10	6.6
Occupation
Farmer	253	30.3	47	13.4	43	41.0	82	74.5	39	32.5	42	27.8	< 0.0001
Employed worker	195	23.3	138	39.4	16	15.2	5	4.5	10	8.3	26	17.2
Trader	155	18.5	66	18.9	24	22.9	2	1.8	35	29.2	28	18.5
Housewife	156	18.7	68	19.4	19	18.1	8	7.3	27	22.5	34	22.5
Casual worker	32	3.8	11	3.1	3	2.9	4	3.6	8	6.7	6	4.0
Other	45	5.4	20	5.7	0	0.0	9	8.2	1	0.8	15	9.9
Missing	2		0		0		0		2		0
Highest education level
None	257	30.7	54	15.4	41	39.0	44	40.0	57	46.7	61	40.4	< 0.0001
Primary	163	19.5	40	11.4	22	21.0	29	26.4	36	29.5	36	23.8
Secondary	209	24.9	99	28.3	24	22.9	31	28.2	21	17.2	34	22.5
Tertiary	209	24.9	157	44.9	18	17.1	6	5.5	8	6.6	20	13.2
Place of residence
Rural	511	61.0	173	49.4	79	75.2	99	90.0	65	53.3	95	62.9	< 0.0001
Urban	327	39.0	177	50.6	26	24.8	11	10.0	57	46.7	56	37.1
Exposure to smoking†
Never exposed	477	56.9	248	70.9	63	60.0	39	35.5	63	51.6	64	42.4	< 0.0001
Exposed	361	43.1	102	29.1	42	40.0	71	64.5	59	48.4	87	57.6
Alcohol use
No	760	90.7	304	86.9	98	93.3	109	99.1	115	94.3	134	88.7	0.0009
Yes	78	9.3	46	13.1	7	6.7	1	0.9	7	5.7	17	11.3
Ethnicity
Bantu	656	78.3	266	76.0	92	87.6	109	99.1	106	86.9	83	55.0	< 0.0001
Nilote	141	16.8	65	18.6	5	4.8	0	0.0	10	8.2	61	40.4
Cushite/Mixed	41	4.9	19	5.4	8	7.6	1	0.9	6	4.9	7	4.6
Reproductive
Age at menarche/year
9–12	68	8.5	30	8.6	10	11.1	7	6.9	7	5.8	14	10.0	0.40
13–14	340	42.4	150	42.9	31	34.4	39	38.2	61	50.8	59	42.1
15–20	394	49.1	170	48.6	49	54.4	56	54.9	52	43.3	67	47.9
Missing	36		0		15		8		2		11
Age at first pregnancy/year
Nulliparous‡	37	4.5	23	6.6	4	3.9	2	1.9	2	1.8	6	4.0	< 0.0001
< 20	216	26.3	62	17.7	29	28.4	34	31.8	38	34.2	53	35.3
20–24	361	44.0	142	40.6	41	40.2	54	50.5	52	46.8	72	48.0
25–29	150	18.3	90	25.7	21	20.6	14	13.1	14	12.6	11	7.3
≥ 30	56	6.8	33	9.4	7	6.9	3	2.8	5	4.5	8	5.3
Missing	18		0		3		3		11		1
Number of children
Nulliparous‡	44	5.3	26	7.4	6	5.7	2	1.8	2	1.6	8	5.3	0.0001
1 or 2	226	27.0	110	31.4	25	23.8	25	22.7	34	27.9	32	21.2
3 or 4	307	36.6	135	38.6	43	41.0	47	42.7	34	27.9	48	31.8
≥ 5	261	31.2	79	22.6	31	29.5	36	32.7	52	42.6	63	41.7
Cumulative breastfeeding duration/month
Nulliparous‡	37	4.6	23	6.6	4	4.0	2	1.9	2	1.7	6	4.2	0.013^a
Never breastfed	7	0.9	3	0.9	2	2.0	0	0.0	0	0.0	2	1.4
Q1: 1−< 39	191	23.5	82	23.7	27	27.0	23	21.3	32	27.8	27	18.9
Q2: 39–< 62	192	23.6	100	28.9	28	28.0	24	22.2	16	13.9	24	16.8
Q3: 62–< 96	182	22.4	80	23.1	17	17.0	28	25.9	24	20.9	33	23.1
Q4: ≥ 96	203	25.0	58	16.8	22	22.0	31	28.7	41	35.7	51	35.7
Missing	26		4		5		2		7		8
Averaged breastfeeding duration per child/month
Nulliparous‡	37	4.6	23	6.6	4	4.0	2	1.9	2	1.7	6	4.2	0.0036^a
Never breastfed	7	0.9	3	0.9	2	2.0	0	0.0	0	0.0	2	1.4
< 12	120	14.8	53	15.3	23	23.0	8	7.4	18	15.7	18	12.6
12–23	407	50.1	153	44.2	46	46.0	71	65.7	64	55.7	73	51.0
≥ 24	241	29.7	114	32.9	25	25.0	27	25.0	31	27.0	44	30.8
Missing	26		4		5		2		7		8
Number of children and cumulative breastfeeding duration
Nulliparous or ≤3 children and < 62 months	354	43.60	179	51.7	44	44.0	43	39.8	44	38.3	44	30.8	< 0.0001
≤ 3 children and ≥ 62 months	79	9.73	43	12.4	5	5.0	10	9.3	8	7.0	13	9.1
≥ 4 children and < 62 months	73	8.99	29	8.4	17	17.0	6	5.6	6	5.2	15	10.5
≥ 4 children and ≥ 62 months	306	37.69	95	27.5	34	34.0	49	45.4	57	49.6	71	49.7
Missing	26		4		5		2		7		8
Age at first pregnancy and number of children
Nulliparous	44	5.36	26	7.4	6	5.8	2	1.9	2	1.8	8	5.3	< 0.0001
Age 25+ years, 1–3 births	154	18.76	98	28.0	16	15.5	13	12.1	13	11.7	14	9.3
Age < 25 years, 1–3 births	244	29.72	101	28.9	27	26.2	38	35.5	37	33.3	41	27.3
Age 25+ years, 4+ births	49	5.97	23	6.6	12	11.7	4	3.7	6	5.4	4	2.7
Age < 25 years, 4+ births	330	40.20	102	29.1	42	40.8	50	46.7	53	47.7	83	55.3
Missing	17		0		2		3		11		1
Menopausal status
Premenopausal	438	52.4	183	52.3	64	61.0	50	45.5	67	55.4	74	49.3	0.18
Postmenopausal	398	47.6	167	47.7	41	39.0	60	54.5	54	44.6	76	50.7
Missing	2		0		0		0		1		1
Age at menopause/year^b
< 50	191	57.4	91	55.8	18	62.1	28	59.6	20	71.4	34	51.5	0.45^b
≥ 50	142	42.6	72	44.2	11	37.9	19	40.4	8	28.6	32	48.5
Missing	65		4		12		13		26		10
Cumulative hormonal contraception exposure/month
< 48	216	45.9	88	46.3	25	44.6	26	40.0	27	34.6	50	61.0	0.014
48	255	54.1	102	53.7	31	55.4	39	60.0	51	65.4	32	39.0
Missing	367		160		49		45		44		69

* P values were computed from chi-square tests except where noted. P values less than 0.05 are shown in bold font. ^a Nulliparous women and parous women who never breastfed were grouped together in chi-square test. ^bChi-square test was performed restricted to postmenopausal women. † Only 3.58% (n=30) of study participants reported ever having smoked or used smokeless tobacco. Exposure to smoking is summarized here as exposed/never exposed, where exposed is defined as personal use of tobacco as well as exposure to smoke at the workplace or home during child or adulthood. ‡ Nulliparous cases were women who reported never pregnant, never given birth, and had no children (N=37, 4.4%). AKU, Aga Khan University; BMI, body mass index; IQR, interquartile range; Q, quartile; SD, standard deviation.

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