Outline X-ray type illustration of a woman with breast cancer.
Credit: SciePro/Fotolia

A simple hormone blood test can identify postmenopausal women who will benefit from preventive breast cancer therapy, shows research led by Queen Mary University of London.

Post-menopausal women with a medium-higher estradiol-sex hormone binding globulin (SHBG) ratio were shown to have increased cancer risk compared to other postmenopausal women. However, preventive treatment with the hormone therapy anastrozole reduced cancer risk in these individuals.

“Measurement of serum hormones is inexpensive, and more routine use of hormone assays in high-risk clinics and for treatment of early breast cancer could substantially improve disease management,” write Jack Cuzick, a professor at the Wolfson Institute of Population Health, Queen Mary University of London, and colleagues in the journal Lancet Oncology.

Breast cancer is a common cancer among women. An average woman in the U.S. has a one in eight chance of developing breast cancer during her lifetime, with risk increasing with increasing age. Evidence shows that post-menopausal women who have higher levels of estrogen in their blood have a higher risk of developing breast cancer than those who do not.

Estrogen reducing therapies such as anastrozole can help reduce the risk of breast cancer in postmenopausal women, but links between individual hormone levels and efficacy of this preventive therapy were less clear.

The current study included 3864 postmenopausal women aged 40–70 years who were categorized as having high breast cancer risk. Of these women, 1920 were given anastrozole and 1944 placebo. The cohort was followed up for 8–13 years.

Rates of breast cancer during follow up were 4.4% in the anastrozole group and 8.5% in the placebo group.

An additional case-control study showed a link between increased estrogen and testosterone levels and cancer risk in the placebo group, but not the treatment group. For each increased quartile of estradiol-SHBG ratio in the placebo group the risk of developing breast cancer increased by 25% versus the lowest quartile. A similar although less significant trend was seen for testosterone-SHBG ratio, with an increased relative risk of 21% per extra quartile.

Further analysis showed anastrozole was effective as a cancer preventive in women with moderate or high levels of estradiol, but not in those in the lowest quartile of the estradiol- SHBG ratio.

“These results are very exciting and can refine how we choose preventive medication for post-menopausal women at high risk of breast cancer,” said lead author Cuzick in a press statement.

“A simple blood hormone test could improve the benefit of anastrozole if we use it to select the patients best suited to take it. We now need to routinely assess hormone levels in postmenopausal women at high breast cancer risk before prescribing anastrozole, to identify those who are at greatest risk and will respond well.”

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