British Journal of Cancer


A population-based cohort study of HRT use and breast cancer in southern
Sweden
H. Olsson, A. Bladström, C. Ingvar, T. R. Möller
p 674-677, Volume 85, Number 5, September 2001
Abstract


The overall tumour incidence and breast cancer incidence related to hormone
replacement therapy (HRT) were followed in a population-based cohort of 29
508 women, aged 25-65 when interviewed in 1990-92. By the end of the follow
up in December 1999, there were 226 611 person-years of observation. A total
of 1145 malignant tumours were recorded (expected 1166.6; SIR = 0.98, 95% CI
0.93-1.04). There was a small excess of breast cancer with 434 observed and
387.69 expected (SIR = 1.12, 95% CI 1.02-1.23). Among about 3 663 ever users
of HRT, there was no increase in overall tumour incidence (SIR = 0.98, 95%
CI 0.86-1.12) but a significant excess of breast cancer (SIR = 1.35, 95% CI
1.09-1.64) compared with never users (SIR = 1.07, 95% CI 0.96-1.19). Breast
cancer increased with increasing duration of use and for 48-120 months use
the SIR was 1.92 (95% CI 1.32-2.70). There was no significant interaction
with family history of breast cancer although an independent additive effect
was suggested between HRT use and family history. In a Cox regression model
time to breast cancer in relation to duration of HRT use was analysed
adjusting for age at menarche, age at menopause, age at first full term
pregnancy, parity and age at diagnosis. A significantly higher risk was seen
for longer duration of HRT use compared with never users. No increased risk
is seen in women beyond 5 years after stopping HRT. There was no interaction
between previous use of oral contraceptives and later HRT use. Copyright
2001 Cancer Research Campaign



Edward E. Rylander, M.D.
Diplomat American Board of Family Practice.
Diplomat American Board of Palliative Medicine.