San Antonio ? Taking menopause hormones for five years doubles the risk for breast cancer, according to a new analysis of a big federal study that reveals the most dramatic evidence yet of the dangers of these still-popular pills.

Even women who took estrogen and progestin pills for as little as a couple of years had a greater chance of getting cancer. And when they stopped taking them, their odds quickly improved, returning to a normal risk level roughly two years after quitting.

Collectively, these new findings are likely to end any doubt that the risks outweigh the benefits for most women.

It is clear that breast cancer rates plunged in recent years mainly because millions of women quit hormone therapy and fewer newly menopausal women started on it, said the study’s leader, Dr. Rowan Chlebowski of Harbor-UCLA Medical Center in Los Angeles.

“It’s an excellent message for women: You can still diminish risk (by quitting), even if you’ve been on hormones for a long time,” said Dr. Claudine Isaacs of Georgetown University’s Lombardi Comprehensive Cancer Center. “It’s not like smoking where you have to wait 10 or 15 years for the risk to come down.”