Reproductive profiles and risk of breast cancer subtypes: a multi-center case-only study

Breast Cancer Research

Table 4 Associations between age at menarche, age at FFTP and breast cancer subtypes

	Luminal B-like Odds ratio (95% CI)^a	P value	Luminal HER2-like Odds ratio (95% CI)^a	P value	HER2-like Odds ratio (95% CI)^a	P value	TNBC Odds ratio (95% CI)^a	P value
Nulliparous women
Age at menarche	Linear model		Linear model		Linear model		Linear model
+ 5 years	1.06 (0.65–1.72)	0.82	1.03 (0.59–1.78)	0.92	1.19 (0.60–2.36)	0.62	1.03 (0.59–1.80)	0.92
Parous women
Age at menarche	Linear model		Linear model		Linear model		Linear model
Menarche (+5 years)	1.04 (0.84–1.28)	0.74	0.99 (0.78–1.25)	0.92	1.16 (0.87–1.56)	0.31	0.99 (0.80–1.23)	0.95
Age at FFTP	Linear model (+5 years)		Linear model (+5 years)		Linear model (+5 years)		Quadratic model
25 versus 20 years							0.78 (0.70–0.88)	<0.0001
30 versus 25 years	1.08 (1.00–1.16)	0.049	1.01 (0.93–1.10)	0.85	1.06 (0.95–1.17)	0.28	0.93 (0.86–1.01)	0.07
35 versus 30 years							1.11 (0.96–1.28)	0.15
Joint analysis age at menarche and age at FFTP
Age at menarche	Linear model		Linear model		Linear model		Linear model
Menarche (+5 years)	1.01 (0.79–1.29)	0.92	0.84 (0.64–1.09)	0.19	1.06 (0.76–1.49)	0.71	1.02 (0.80–1.29)	0.90
Age at FFTP	Linear model (+5 years)		Linear model (+5 years)		Linear model (+5 years)		Quadratic model
25 versus 20 years							0.78 (0.69–0.88)	<0.0001
30 versus 25 years	1.07 (0.99–1.16)	0.10	0.99 (0.91–1.09)	0.91	1.03 (0.92–1.15)	0.62	0.92 (0.85–1.00)	0.045
35 versus 30 years							1.09 (0.94–1.26)	0.27

The results of logistic regression models are reported for each breast cancer (BC) subtype while considering luminal A BC as a reference (the binary response takes values 0 for luminal A or 1 for the subtype that is considered), age at menarche or age at first full-term pregnancy (FFTP) are considered explanatory variables. A random intercept was introduced to account for clustering by study. All analyses reported in this section were performed with correction for age at diagnosis as a continuous variable). Age at menarche or age at FFTP were modeled linearly (for age at menarche), whereas linear and quadratic functions were considered for age at FFTP. The best fit was tested (as described in “Methods”) and are reported here
HER2 human epidermal growth factor receptor-2, TNBC triple negative breast cancer, CI confidence interval, FFTP first full-term pregnancy
^aAdjusted for age at diagnosis

ISSN: 1465-542X