No increased death toll for long-term MHT
25 September 2017:
The saga of the Women's Health Initiative (WHI) seems to have come to a turning point with a declaration that should vibrate now throughout the whole world. A new release of data from the WHI study has concluded that 'Among postmenopausal women, hormone therapy with CEE [conjugated equine estrogen] plus MPA [medroxyprogesterone acetate] for a median of 5.6 years or with CEE alone for a median of 7.2 years was not associated with risk of all-cause, cardiovascular, or cancer mortality during a cumulative follow-up of 18 years' [1]. Amazing as it is, the safety concerns that were attributed in the past to menopausal hormone therapy (MHT) need to be re-considered and to be put in their right perspective. It is not necessary to present again the main features of the CEE + MPA and the CEE-alone randomized studies.
The main issues discussed by the WHI investigators included the following:
- The present report is based on mortality follow-up through December 2014 and includes 7489 deaths (1088 occurred during the intervention phase and 6401 occurred post-intervention; 4083 additional deaths had occurred since the last report). For the CEE + MPA trial, the median post-intervention follow-up was 12.5 years and the cumulative follow-up was 18 years; for the CEE-alone trial, the median post-intervention follow-up was 10.8 years and the cumulative follow-up was 18 years.
- During the intervention phase, all-cause mortality in the pooled cohort was 4.0% with hormone therapy vs. 4.0% with placebo. Compared with placebo, women randomized to receive CEE + MPA had a hazard ratio (HR) of 0.97 (95% confidence interval (CI) 0.82–1.16) and women randomized to receive CEE alone had a HR of 1.04 (95% CI 0.89–1.22). During the post-intervention period, the HR for all-cause mortality was 1.04 (95% CI 0.97–1.10) for CEE + MPA and 0.92 (95% CI 0.85–0.99) for CEE alone.
- The HRs for all-cause mortality tended to differ by age during the intervention and cumulative follow-up phases. Comparison of women aged 50–59 years with those aged 70–79 years showed that the risk was significantly lower for the younger age group, as ratios of nominal HRs for all-cause mortality in the pooled cohort were 0.61 (95% CI 0.43–0.87) during the intervention phase and 0.87 (95% CI 0.76–1.00) during cumulative 18-year follow-up, without significant heterogeneity between trials. Although younger women tended to have lower HRs than older women for mortality due to cardiovascular disease (CVD), cancer, and other (non-CVD, non-cancer) causes during the intervention phases of the two trials, only the latter outcome in the CEE-alone trial showed a statistically significant trend with age (p for trend by age = 0.002). During cumulative follow-up, trends in cause-specific mortality across age groups were not statistically significantly different.
In the Discussion section, the investigators had several important comments as well. They claimed that no other randomized clinical trial of hormone therapy has been large enough to assess a potentially modifying effect of age on all-cause mortality. They noted that observational studies, which primarily include women who initiate hormone therapy in early menopause, have generally demonstrated lower mortality among women using hormone therapy compared with non-users. HRs in most large cohort studies have ranged from 0.40 to 0.80. Regarding cause-specific mortality, the most marked risk reductions reported in observational studies have been for coronary or CVD deaths. Total cancer mortality did not differ significantly between intervention and placebo groups in either trial despite the increased incidence of breast cancer with CEE + MPA. However, a significant reduction in breast cancer was seen with CEE. Divergent findings for CEE alone and CEE + MPA for breast cancer point to an adverse effect of progestin on the breast epithelium, but progestins have been linked to favorable effects on the endometrium, and a decreased risk of endometrial cancer became apparent with long-term follow-up of the CEE + MPA trial. Last, but not least, it was mentioned that only one dose, formulation and route of administration in each trial were assessed; thus, results cannot necessarily be generalized to other hormone preparations.