Short answer: Yes. Estrogen labels say estrogen alone and estrogen with a progestin have been linked to more abnormal mammograms that need follow-up. In the Women's Health Initiative, about 9% of women on hormones had an abnormal mammogram after 1 year, against about 5.5% on placebo. The labels list a yearly breast exam and mammograms scheduled by age, risk and past results.
The Prempro, Premarin, Climara and Vivelle-Dot labels share one sentence in their breast cancer warning: the use of estrogen alone and estrogen plus progestin has been reported to increase abnormal mammograms requiring further evaluation (section 5.2 or Warnings). They add that all women should have a yearly breast exam by a clinician and do monthly self-exams, and that mammograms should be scheduled based on age, risk factors and prior results.
The Prempro Patient Information puts it plainly: a pelvic exam, breast exam and mammogram every year unless the healthcare provider says otherwise, and more often for women with breast lumps, an abnormal mammogram or breast cancer in the family.
| Trial | Women | After 1 year | Other findings |
|---|---|---|---|
| Estrogen plus progestin (Chlebowski 2003) | 16,608 women aged 50 to 79 with a uterus | 9.4% vs 5.4% on placebo | More invasive breast cancers (199 vs 150), found at a larger size and later stage |
| Estrogen alone (Stefanick 2006) | 10,739 women aged 50 to 79 after hysterectomy | 9.2% vs 5.5% on placebo | Over the trial, 36.2% vs 28.1% had an abnormal result, mostly short-interval follow-up; invasive breast cancer was not raised (hazard ratio 0.80, not significant) |
Both trials used oral conjugated estrogens, 0.625 mg a day, with 2.5 mg medroxyprogesterone in the combined arm. The authors of the combined trial wrote that estrogen plus progestin may make breast cancer harder to find on a mammogram.
An abnormal mammogram is a result that needs another look, such as extra images, an ultrasound or a short-interval repeat. It is not a cancer diagnosis. In the estrogen-alone trial, the extra abnormal results were mostly of the short-interval follow-up kind.
The labels do not say to stop hormones before a mammogram, and they do not set a separate screening schedule for hormone users beyond the yearly breast exam and mammograms timed to age, risk and past results.
Whether to start or continue hormone therapy weighs symptom relief against risks, which the labels say to review regularly, using the lowest effective dose for the shortest time that fits the goals. Family history and past breast problems are part of that conversation. Dose Track keeps the product, dose and start date in one place, which is the history a radiologist or prescriber may ask about.
Read more on Dose Track: Prempro side effects · Prempro dosing schedule · Women's Health Initiative · Menopause