Estrogen Matters: Why Taking Hormones in Menopause Can Improve Women's Well-Being and Lengthen Their Lives -- Without Raising the Risk of Breast Cancer (2024 Revised and Updated Edition)

by Carol Tavris

The WHI investigators reported that women who were randomly assigned to take estrogen on its own had had no increased risk of breast cancer. Those who still had a uterus and were assigned to take the combination of estrogen and progestin (HRT) had a small increased risk of breast cancer (of 1.26) when compared with women who were randomly assigned to a placebo.33 That number, 1.26, means a 26 percent increase in risk. Few noticed this sentence: “The 26 percent increase in breast cancer incidence among the HRT group compared with the placebo group almost reached nominal statistical significance.” Almost means it did not reach statistical significance, and that means it could have been a spurious association.