AIM: The use of hormone replacement therapy (HRT) can lead to various chang
es on the mammogram including increasing density, The object of this study
was to assess the effect of HRT on the sensitivity of mammographic screenin
g by comparing HRT usage in women with screen detected breast cancers with
HRT usage at the time of screening in women presenting with interval cancer
s.
METHODS: The West of Scotland Breast Screening Programme serves a populatio
n of 180,000 women aged 50-64 Sears old, Between May 1988 and December 1995
, 1461 breast cancers were detected by the screening programme in 1441 wome
n over the age of 50 and 372 interval breast cancers presented in 371 women
screened between these dates, HRT usage at the time of screening was noted
with details of age, postcode and the time between screening and diagnosis
in the case of the women with interval cancers.
RESULTS: Among women under 65 years old, screened between 1988-1993, 12.3 %
of women with screen detected cancers and 22.2% of women Kith interval can
cers were using HRT (P<0.001). Further analysis demonstrates that interval
cancer rate is related to age as well as HRT use. After adjusting for age a
t time of screening, deprivation category and year of screening, the relati
ve risk of a woman using HRT having an interval cancer compared with that o
f a woman not using HRT is 1.79. The relative risk of an interval cancer ar
ising in the first year after screening for a woman on HRT is 2.27,
CONCLUSION: The use of HRT and being of an age below 60 years are both risk
factors for presenting with an interval cancer after mammographic breast s
creening. Our results indicate that the use of HRT leads to a decrease in t
he sensitivity of mammographic screening.