Recreational physical activity and risk of triple negative breast cancer in the California Teachers Study

Breast Cancer Research

Table 3 Adjusted hazard ratios for the associations between strenuous recreational physical activity and invasive breast cancer subtypes by body mass index at baseline

BMI, kg/m²	Cases, no.	Strenuous RPA, h/wk/y			P _trend	P _{homogeneity of trends}
	Cases, no.	≤0.50	0.51–3.50	≥3.51	P _trend	P _{homogeneity of trends}
		Adjusted HR (95 % CI)	Adjusted HR (95 % CI)	Adjusted HR (95 % CI)
Among all women
TNBC (ER-/PR-/HER2-)
Long-term^a
BMI <25	195	Referent	0.88 (0.64–1.22)	0.62 (0.39–0.99)	0.05	0.54
BMI ≥25	139	Referent	0.85 (0.59–1.24)	0.78 (0.45–1.36)	0.37
Baseline^b
BMI <25	195	Referent	1.04 (0.76–1.42)	0.60 (0.37–0.97)	0.05	0.40
BMI ≥25	139	Referent	0.72 (0.47–1.10)	0.48 (0.21–1.10)	0.04
Luminal A-like (ER+ or PR+ plus HER2-)
Long-term^a
BMI <25	1484	Referent	0.95 (0.84–1.07)	0.93 (0.79–1.09)	0.39	0.71
BMI ≥25	1119	Referent	0.87 (0.76–0.99)	0.90 (0.74–1.08)	0.25
Baseline^b
BMI <25	1484	Referent	0.89 (0.79–1.00)	0.88 (0.76–1.03)	0.08	0.31
BMI ≥25	1119	Referent	0.87 (0.75–1.00)	1.06 (0.86–1.32)	0.99
Among peri- and postmenopausal women at baseline
TNBC (ER-/PR-/HER2-)
Long-term^a
BMI <25	118	Referent	1.01 (0.67–1.53)	0.78 (0.41–1.47)	0.45	0.99
BMI ≥25	89	Referent	0.89 (0.56–1.43)	0.83 (0.40–1.73)	0.60
Baseline^b
BMI <25	118	Referent	1.26 (0.83–1.90)	0.69 (0.35–1.36)	0.42	0.06
BMI ≥25	89	Referent	0.56 (0.31–1.02)	0.28 (0.07–1.17)	0.02
Luminal A-like (ER+ or PR+ plus HER2-)
Long-term^a
BMI <25	940	Referent	0.97 (0.84–1.12)	0.90(0.73–1.12)	0.34	0.39
BMI ≥25	794	Referent	0.86 (0.73–1.00)	0.80(0.63–1.02)	0.06
Baseline^b
BMI <25	940	Referent	0.93 (0.80–1.09)	0.86 (0.70–1.05)	0.13	0.47
BMI ≥25	794	Referent	0.90 (0.75–1.07)	1.01 (0.77–1.32)	0.78

HRs are from multivariable Cox proportional hazards regression models using age (in days) as the time metric and stratified by age (in years) with the adjustment for race, family history of breast cancer in first-degree relatives, combined age at first full-term pregnancy and parity variable, combined menopausal status and MHT use variable, history of smoking, alcohol intake during the past year of baseline, screening mammogram in the past 2 years of baseline, history of a breast biopsy, and a corresponding moderate RPA variable
Abbreviations: BMI body mass index, CI confidence interval, ER estrogen receptor, HER2 human epidermal growth factor receptor 2, HR hazard ratio, h/wk/y hour/week/year, MHT menopausal hormone therapy, PR progesterone receptor, RPA recreational physical activity, TNBC triple negative breast cancer
^aRPA from high school till age 54 or age at cohort entry, whichever was younger
^bRPA during the 3 years prior to baseline

ISSN: 1465-542X