A gel containing the drug tamoxifen and applied to the skin was as effective in reducing the growth of breast cancer cells in women with noninvasive cancer as the pill form of the medication — and it caused fewer side effects, according to a new study.
The paper, published Tuesday in Clinical Cancer Research, a journal of the American Association for Cancer Research, said that the gel was applied to the breasts of women diagnosed with ductal carcinoma in situ, or DCIS. All the women had DCIS that was sensitive to estrogen.
After six to 10 weeks of gel application, the reduction in a marker for cancer cell growth in the breast tissue was similar to that of the orally administered tamoxifen, the study found.
The findings could have broad implications, the researchers said. The gel, like the pill form of the drug, could be used to reduce the risk of a recurrence of breast cancer or to try to prevent the disease in the first place.
But it might be used more widely because it causes fewer side effects, said Seema Khan, a surgical oncologist at the Northwestern University Feinberg School of Medicine in Chicago, and the lead author of the study.
Tamoxifen is a used to treat women with estrogen receptor-positive cancer, which relies on estrogen to grow. When taken for five years, the drug can cut in half the risk of recurrence of this type of cancer.
Tamoxifen’s side effects range from hot flashes and vaginal dryness to potentially fatal blood clots and uterine cancer.
The medicated gel causes fewer side effects because the drug is concentrated in the breast tissue, and doesn’t circulate much 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.”
The study could have broader implications for other drugs that cannot be administered by mouth but might be safely used topically.
A related study released Tuesday said that researchers have identified the genes that help predict whether patients will respond to tamoxifen. About one-third of women with estrogen receptor-positive breast cancer relapse after being treated with tamoxifen and, even with further treatment, have a median survival rate of 30 to 45 months.
“It has been very difficult to identify patients whose tumors lack a proper response to tamoxifen,” said René Bernards, professor and head of the Division of Molecular Carcinogenesis at the Netherlands Cancer Institute in Amsterdam.
Using data from about 680 patients, the researchers are doing further testing on the effectiveness of the gene signature in predicting whether women at risk would respond to tamoxifen therapy.