Hormone therapy raises the risk of breast cancer in women who develop new-onset breast tenderness after starting estrogen plus progestin hormone replacement therapy, according to a new research.

The study examined breast tenderness and the occurrence of cancer in more than 16,000 patients in the Women’s Health Initiative estrogen-plus-progestin clinical trial.

Women on the hormone therapy who did not have breast tenderness were compared with those who were on placebo at the start of the trial and it was found that the former was three times more likely to develop breast tenderness after one year.

It was observed further that this group experienced a 48 percent higher risk of invasive breast cancer than those on the combination therapy who did not report tenderness after one year.

“Hormone therapy is causing breast-tissue cells to multiply more rapidly, which causes breast tenderness, leading to a greater risk of developing cancer”, as hypothesized by Dr. Carolyn J. Crandall, who is UCLA study’s lead researcher.

The trial was stopped in 2002 by the researchers soon after they found that the combination therapy led to an elevated cancer risk in healthy menopausal women.

The Centers for Disease Control and Prevention report that a total of 41,116 women and 375 men died from breast cancer in 2005.