Table 3.

Joint relation of years since last use and duration of use to breast cancer incidence by receptor status

UsePerson-yearsER+/PR+ER+/PRER/PR
Years since last useDuration (y)No. casesIRR (95% CI)No. casesIRR (95% CI)No. casesIRR (95% CI)
Never used128,7681021.00 (reference)*291.00 (reference)461.00 (reference)
<5<554,784100.89 (0.45-1.77)51.77 (0.63-4.99)121.54 (0.78-3.05)
5-942,284101.19 (0.59-2.40)41.92 (0.60-6.19)91.58 (0.73-3.42)
10+42,824241.66 (1.01-2.74)30.84 (0.23-13.03)222.52 (1.43-4.45)
5-9<524,427122.13 (1.13-4.03)10.72 (0.09-5.50)41.03 (0.36-2.94)
5-912,57441.03 (0.37-2.89)0-31.15 (0.35-3.80)
10+12,28381.31 (0.62-2.77)31.85 (0.53-6.47)321.50 (0.58-3.86)
10+<5171,4371281.00 (0.76-1.32)370.86 (0.52-1.44)1231.72 (1.21-2.44)
5-955,285501.10 (0.77-1.57)211.35 (0.75-2.46)321.35 (0.85-2.15)
10+29,927381.33 (0.90-1.95)60.64 (0.26-1.58)231.69 (1.01-2.83)
  • *Never use of oral contraceptives is the reference category; IRRs are adjusted for age, age at menarche, BMI at age 18 y, family history of breast cancer, education, parity, age at first birth, menopausal status, age at menopause, menopausal hormone use, vigorous activity, and alcohol intake.