When added to conventional hormone replacement therapy (HRT), testosterone may reduce the risk of breast cancer in postmenopausal women, results of a small study suggest.

“I hope that this paper stimulates interest in the question of whether a more physiological HRT regimen might have better effects,” senior author Dr. Carolyn A. Bondy told Reuters Health.

But, she emphasized, “I do not recommend any changes in HRT treatment until we’re convinced it’s safe and efficacious.”

The Women’s Health Initiative and the “Million Women” Study, large clinical trials of combined estrogen and progestin HRT, were terminated early when they showed an increased risk of breast cancer. However, these studies did not evaluate combined treatment that included testosterone.

Bondy, with the National Institutes of Health in Bethesda, Maryland, and colleagues report the results of a look-back study of 508 postmenopausal women given testosterone and estrogen, with or without progestin, for an average of about 6 years. Their findings are published in the medical journal Menopause.

During follow-up there were seven cases of invasive breast cancer. One case occurred in the group using estrogen and testosterone only, while six cases occurred in the group that was also using progestins - which translates to about twice the incidence.

In comparison, the incidence of breast cancer was 2- to 3- times higher among women taking estrogen and progestin arm of the Women’s Health Initiative.

Before menopause, the ovaries produce both testosterone and estrogen, co-author Dr. Robert A. Jones, at Memorial Medical Center in North Adelaide, South Australia, explained in an interview with Reuters Health. Conventional HRT “tends to interfere with the protective effect of testosterone,” thus increasing the risk of breast cancer.

“If testosterone had been used by subjects in the Women’s Health Initiative study, it may have stopped the rise in breast cancer risk,” he added. “It’s possible the trial would not have needed to be stopped early.”

His group’s findings also confirm the suspected increased risk when oral progestin is added to estrogen HRT. That issue could possibly be circumvented by administering the progestin via an intrauterine device rather than orally, Jones said. After all, he commented, “Why give progestin to the breast when all you want to do is give it to the uterus?”

He noted that testosterone has the added bonus of improving a woman’s mood, reducing breast soreness, increasing bone density, as well as restoring energy, stamina, and sex drive.

In the end, though, these findings do not prove that testosterone is protective, Jones added.

Bondy agreed. “I would love to see a clinical trial, especially for younger women who’ve had their ovaries surgically removed or who have ovarian failure for some other reason, who have to take HRT. Otherwise, they get terrible osteoporosis and their sexual characteristics disappear at a young age.”

Until such studies have been completed, she reiterated, “I do not want people to jump on the bandwagon and do something that is unproven.”

SOURCE: Menopause, September/October 2004.