Does Hormone Replacement Therapy Cause Breast Cancer?
Does Hormone Replacement Therapy Cause Breast Cancer?
Among 828 923 postmenopausal women followed for an average of 2.6 years the RRs of invasive breast cancer for current and past users of HRT were 1.66 and 1.01 (95% CI, 0.94–1.09). Among women currently using HRT at baseline the RRs for users of various types of HRT were as follows: ET, 1.30; E+P, 2.00; tibolone, 1.45; other or unknown HRT, 1.44. The difference between E+P vs ET was significant (p<0.0001).
For current ET use at baseline the RRs for <5 and ≥5 years' total duration were 1.21 and 1.34, and for E+P use, 1.70 and 2.21. For ET use the RRs for total durations of <1, 1–4, 5–9 and ≥10 years of use were 0.81 (95% CI, 0.55–1.20), 1.25, 1.32 and 1.37; for E+P use they were 1.45, 1.74, 2.17 and 2.31.
Among women who last used HRT ≤1 year previously the RR was 1.14; for exposures that ended 2–≥10 years previously the RRs approximated unity. The average time to diagnosis was 1.2 years, and within 1.7 years of diagnosis the RR of fatal breast cancer was 1.22.
The investigators estimated that the "use of HRT by UK women aged 50–64 years … resulted in an extra 20 000 incident breast cancers, combined [E+P] accounting for 15 000" of them. They also estimated that HRT would "result in five to six extra cancers per 1000 women with 5 years' use and 15–19 … per 1000 with 10 years' use". They concluded that "current use of HRT is associated with an increased risk of incident and fatal breast cancer" … [which is] … "substantially greater for [E+P] combinations than for other types of HRT".
First Report (2003)
Among 828 923 postmenopausal women followed for an average of 2.6 years the RRs of invasive breast cancer for current and past users of HRT were 1.66 and 1.01 (95% CI, 0.94–1.09). Among women currently using HRT at baseline the RRs for users of various types of HRT were as follows: ET, 1.30; E+P, 2.00; tibolone, 1.45; other or unknown HRT, 1.44. The difference between E+P vs ET was significant (p<0.0001).
For current ET use at baseline the RRs for <5 and ≥5 years' total duration were 1.21 and 1.34, and for E+P use, 1.70 and 2.21. For ET use the RRs for total durations of <1, 1–4, 5–9 and ≥10 years of use were 0.81 (95% CI, 0.55–1.20), 1.25, 1.32 and 1.37; for E+P use they were 1.45, 1.74, 2.17 and 2.31.
Among women who last used HRT ≤1 year previously the RR was 1.14; for exposures that ended 2–≥10 years previously the RRs approximated unity. The average time to diagnosis was 1.2 years, and within 1.7 years of diagnosis the RR of fatal breast cancer was 1.22.
The investigators estimated that the "use of HRT by UK women aged 50–64 years … resulted in an extra 20 000 incident breast cancers, combined [E+P] accounting for 15 000" of them. They also estimated that HRT would "result in five to six extra cancers per 1000 women with 5 years' use and 15–19 … per 1000 with 10 years' use". They concluded that "current use of HRT is associated with an increased risk of incident and fatal breast cancer" … [which is] … "substantially greater for [E+P] combinations than for other types of HRT".
