A new study by researchers at the Institute of Cancer Research has substantiated that hormone replacement using estrogen and progesterone increases the risk of breast cancer, especially with longer use.
British Journal of Cancer
Hormone-replacement therapy, commonly called HRT, is used to overcome lifestyle-disrupting symptoms associated with menopause, including hot flushes, migraines, mood changes, depression. However, there’s been a lot of controversy about the safety of HRT, with evidence of increased risk of cancer. Now, a new study in the has confirmed the risk following a 6-year follow up in nearly 40,000 women.
In their study, researchers from the Institute of Cancer Research recruited more than 113,000 women between June 2003 and December 2009 for a 6-year follow-up study; of these, more than 58,000 had reached menopause during the follow-up period and 96% completed a follow-up questionnaire at 2.5 years and 6 years after recruitment. However, the actual menopausal age was known for only 39,183 women. The authors categorized the follow-up period after onset of menopause as before menopausal hormonal therapy (MHT) use, current MHT use, and after cessation of MHT use (which could happen during work-up to a potential breast cancer diagnosis).
In their cohort, 5% of women who had not used MHT by recruitment used it sometime during the follow-up period, and 65.4% of current users ceased use of estrogen-only MHT by the end of follow up. Women who were recruited for this study had used estrogen-only MHT for a median 6.5 years (range 2.5 to 10.5 years), estrogen and progesterone MHT for a median 5.5 years (range 2.5 to 9.5 years), while other types of MHT were used for a median period of 4.5 years (range 1.5 to 8.5 years).
The authors found that the hazard ratio (HR) for invasive and in situ breast cancer was 1.95 (95% CI, 1.55-2.46; <.001) for current users of MHT compared with never users, and this ratio grew with increasing number of years of usage. For women who used MHT for more than 15 years, the HR was 2.02 (95% CI, 1.12-3.66; = .020). While estrogen-only MHT preparations did not significantly increase the risk of breast cancer following a median use of 6.6 years (HR=1.00; 95% CI, 0.66-1.54; = .99), combined use of estrogen and progesterone cause a significant increase in the risk of breast cancer (HR=2.74; 95% CI, 2.05-3.65; <.001), with a 5.6% increase in HR per year of use that reached 3.27 at more than 15 years of use.
“Our research shows that some previous studies are likely to have underestimated the risk of breast cancer with combined estrogen-progestogen HRT,” said senior author of the study, Anthony J Swerdlow, PhD, MPH, professor at the Institute of Cancer Research, in an interview. “Our findings provide further information to allow women to make informed decisions about the potential risks and benefits of HRT use,” he added.
The findings should encourage women to discuss the potential risks and benefits of using HRT with their physician to make informed decisions about initiating treatment.
Br J Cancer
Jones ME, Schoemaker MJ, Wright L, et al. Menopausal hormone therapy and breast cancer: what is the true size of the increased risk [published online July 28, 2016]? . doi: 10.1038/bjc.2016.231.