Tamoxifen Provides Long-Term Protection against Breast Cancer

Tamoxifen is a primary breast cancer prevention treatment that is known for a long time to be effective. A new study suggests that the drug appears to be more effective with more applications and dosages over the long term.

Researchers have found that taking the drug for five years reduces the incidence of breast cancer in women at high risk for the disease by close to 30 per cent. In addition, the medication's protective effects against breast cancer appear to last for as long as 16 years after a woman stops taking it, according to Sci-Tech Today.

The IBIS-I trial (International Breast Cancer Intervention Study-I) found that tamoxifen was even more effective in preventing breast cancer in women who did not take hormone replacement medications, with 38 per cent decline in breast cancer diagnoses of any genetic variety over roughly 16 years of follow-up. In addition, new diagnoses of estrogen-sensitive breast cancers -- the most common kind -- dropped by 45% among these women.

Jack Cuzick, PhD, of Queen Mary University of London said: "With an additional 10 years of follow-up we have substantially larger differences which bodes well for the prospects that the prevention may even be longer than 20 years-potentially a lifetime."

Less than 10 per cent of the women who had breast cancer have died from it. It's actually probably too early to make any pronouncements, favorable or unfavorable, about deaths from breast cancer. That's actually going to take another 10 years of follow-up," he added.

According to Northwestern University's William Gradishar, MD, although chemoprevention with tamoxifen works, there are still risks when using any drug, reported the Diabetes Insider.

Only 5% of the 7,154 IBIS subjects -- who were between 35 and 70 at the study's start -- have died, and there were only 31 breast cancer deaths among the 3,579 women who took tamoxifen.

However, IBIS-I trial did turn up a worrisome finding that women taking tamoxifen are at slightly greater risk of developing endometrial cancers. This is a long-recognized trend that raises few concerns because such cancers tend to be slow-growing and readily treatable.

The IBIS-I study was published in the journal Lancet Oncology.