Cancer risk from HRT remains long after treatment has stopped

Mar 5 2008

The results of a new study have shown that the risk of cancer associated with Hormone Replacement Therapy (HRT) continues long after a woman stops taking it.

In 2002 the Women's Health Initiative (WHI) study was stopped following the discovery of a significant increased risk of breast cancer and heart and artery disease in women assigned HRT.

The trial had been running for around five years and involved 16,608 healthy post-menopausal women with an average age of 63, who were either given a combination oestrogen/progestin hormone replacement treatment or an inactive placebo.

It was this trial which alerted the world to the dangers of HRT and as a result millions of women worldwide stopped taking the therapy.

After the trial stopped almost 15,730 of the women continued to be monitored for a further three years to see what effect ceasing treatment may have made.

The researchers found that their breast cancer risk was still raised by 27% three years after treatment ceased, and their chances of developing any type of cancer were 24% above average.

On a more positive note however the risk of heart attacks, strokes and blood clots and strokes were similar in both the active and placebo treatment groups and the risk of cardiovascular disease had fallen substantially for former HRT users.

During the trial the women taking HRT experienced a 29% increased risk of heart attacks, a 41% increased risk of strokes and nearly twice the normal risk of serious blood clots.

During the follow-up study there were 63 more diagnoses of cancer among former HRT users than among women who did not have the treatment, or three per 1,000 participants per year.

The researchers say clinical vigilance is advisable because of the higher risk of malignancies for a period of 3.5 to 8.5 years, following the termination of HRT.