Tamoxifen, a hormone drug that blocks the effects of estrogen on breast tissues which could otherwise cause cancer cells to divide and grow, is prescribed for women with increased risks for breast cancer and as treatment for those who are already diagnosed with the condition.

Although the drug is a mainstay in breast cancer prevention and treatment, tamoxifen, which is currently taken orally, is associated with unwanted side effects such as increased risks for blood clots, stroke and cancer in other tissues, which explains why some patients are cautious to take the drug. A new study, however, suggests that the drug in gel form can be as effective and is even associated with fewer side effects compared with the oral form of tamoxifen.

For the study published in the Clinical Cancer Research on July 15, Seema Khan, from the Northwestern University Feinberg School of Medicine, and colleagues conducted a study on 27 women with ductal carcinoma in situ (DCIS), the most common type of breast cancer. Women with DCIS are often advised to take tamoxifen to prevent recurrent growths.

The researchers gave half of the participants the pill form of the drug and the other half were given the gel form that was applied directly to the breast tissue for six to 10 weeks prior to their surgery. Khan and colleagues then analyzed the women's breast tissues for tumor growth and their blood for tamoxifen levels.

They found that women in both groups had similar reduction in cancer cell growth but the women who took the oral form of the drug were found to have five times more amount of tamoxifen in their blood compared to women who had used the drug in gel form.

"The antiproliferative effect of 4-OHT gel applied to breast skin was similar to that of oral-T, but effects on endocrine and coagulation parameters were reduced," Khan and colleagues wrote. "These findings support the further evaluation of local transdermal therapy for DCIS and breast cancer prevention."

The researchers said that the gel has fewer side effects because it was concentrated in the breast tissue and are not circulating in high concentration in the blood.

"The gel minimized exposure to the rest of the body and concentrated the drug in the breast where it is needed," Khan said. "There was very little drug in the bloodstream, which should avoid potential blood clots as well as an elevated risk of uterine cancer."