The most powerful regimen against breast cancer since tamoxifen has been discovered by researchers at the University of Oxford, and it's a combination of two available, inexpensive generic drugs called aromatase inhibitors and bisphosphonates.

The research, which was published in The Lancet, found that aromatase inhibitors substantially reduced the risk of death from breast cancer in postmenopausal women when compared with tamoxifen in women with the most common form of the disease.

More than 80 percent of cases of breast cancer that occur after menopause are ER-positive, which means the cancer has receptors for estrogen that help promote the its growth. Aromatase inhibitors suppress the manufacture of estrogens in the body and are taken by postmenopausal women with hormone-sensitive (ER-positive) breast cancer.
Previous studies have found they reduce the risk of recurrence more than tamoxifen, but no increase in survival has been proven.

The current study combined results from 31,920 women in nine clinical trials. It showed that taking aromatase inhibitors for five years reduced the risk of postmenopausal women with ER-positive breast cancer dying from their disease by 40 per cent within 10 years of starting treatment, compared with no hormonal treatment. Women who took tamoxifen for five years reduced their risk by 30 percent.

"Aromatase inhibitors remove only the tiny amount of estrogen that remains in the circulation of women after the menopause — but that's enough to have a substantial impact on a wide range of ER-positive tumors" said Mitch Dowsett, the study's lead author.

Another study involving bisphosphonates was published in the same issue of The Lancet. It found bisphosphonates, which are drugs sued to treat osteoporosis, could prevent one in six breast cancers in postmenopausal women, and reduce the risk of dying from breast cancer by 18 percent in the 10 years following diagnosis. The cheap, widely available drugs keep breast cancer from spreading to the bones, the most common site breast cancers spread to.

The two studies suggest that aromatase inhibitors and bisphosphonates could be used together to help fight the disease

"These studies provide really good evidence that both of these inexpensive, generic drugs can help to reduce breast cancer mortality in postmenopausal women," said Richard Gray of the University of Oxford, who was the lead statistician for both studies.

"About two-thirds of all women with breast cancer are postmenopausal with hormone-sensitive tumors, so could potentially benefit from both drugs," Gray said. "The drugs are complementary, because the main side effect of aromatase inhibitors is an increase in bone loss and fractures, while bisphosphonates reduce bone loss and fractures as well as improve survival."