Combined estrogen and progestogen therapy is associated with a small increase in risk that grows with duration of use. Estrogen alone has not shown that association and in the WHI showed slightly lower incidence. Association at this scale is not the same as cause, and the absolute numbers are small.
What 2002 found
Los Angeles safety review: the trial, and what it actually measured
Almost every fear a Los Angeles patient brings to this subject traces back to one trial and the headlines that followed it in 2002. The Women's Health Initiative combined arm was halted early in 2002 after reporting a small increase in breast cancer and cardiovascular events. Prescriptions fell by more than half within a year.
The detail that did not make the coverage was the population. The average participant was 63 years old and more than a decade past menopause, and the medicines studied were oral conjugated equine estrogen with a synthetic progestin.
That is not the woman starting a transdermal estradiol patch at 49 with micronized progesterone. The trial answered a question about a different population taking different drugs, which is why the age-stratified re-analysis matters so much. More on that in safety and risks, heart health after menopause and early and surgical menopause. When a Los Angeles clinician quotes that trial, the question worth asking is which women it enrolled and which drugs they were actually given.
