Tamoxifen Gel May Cause Fewer Blood Clots

Breast cancer patients may benefit from metabolite of tamoxifen in gel form

/ Author:  / Reviewed by: Joseph V. Madia, MD Beth Bolt, RPh

(RxWiki News) Women with a certain type of breast cancer may be prescribed a medication called tamoxifen to slow the spread of the cancer. In some women, though, tamoxifen causes harmful side effects. A similar medication may lead to fewer such side effects.

A recent study found that a product of tamoxifen in gel form (4-OHT) worked as well as the oral form (Rheumatrex, Soltamox, Nolvadex, Trexall) with fewer cases of blood clots.

"If you have breast cancer, discuss treatment options with your oncologist."

This research was led by Oukseub Lee, a research associate at the Robert H. Lurie Cancer Center of Northwestern University in Chicago.

Lee and colleagues reported on results of a phase II trial, which is when a medication is tested for effectiveness and safety.

For the trial, 26 women aged 45 to 86 years, were enrolled. All had ductal carcinoma in situ (DCIS) of the breast, which is a cancer in the milk duct. In DCIS, the cancer has not yet spread, but if there are receptors on the cells for estrogen, the cancer has the potential to grow.

The women in this study were given treatment before surgery. They were all to have surgery to remove the part of their breast that was cancerous.

Tamoxifen blocks activity of estrogen in the breast, helping to reduce the risk of developing a more serious type of breast cancer.

The women received treatment for six to 10 weeks. Of the 26 women, 14 received 20 milligrams per day of oral tamoxifen. Twelve women had 4 milligrams of the 4-OHT gel applied to their breasts each day, 2 milligrams per breast.

The women did not know which form of the medication they received, since all received pills and gel. In some women, the pills did not contain tamoxifen, and in others, the gel did not contain 4-OHT.

All patients gave blood for testing at the start of the study and completed a questionnaire. They then had a repeat blood test at the end of the study. They completed similar questionnaires at the end of the study and during a visit after surgery. The questionnaires asked about symptoms like hot flashes and pain.

The researchers checked for levels of an antibody marker in the breast tissue that showed how quickly cancer cells were growing and dividing. At the end of the study, women who received the 4-OHT gel had a similar number of these markers compared to women who received oral tamoxifen.

Women who had been treated with the gel, however, had about a five-fold lower level of the antibody in their blood. When circulating in the blood, the antibody can cause potentially dangerous blood clots. A lower level of the antibody reduces the likelihood of blood clots.

However, the study authors found that some side effects, including hot flashes, vaginal symptoms, gastrointestinal symptoms and sweats, were the same in both groups.

The authors noted that the sample of women was small because there was limited availability of the medication. Furthermore, although clinicians thought that waiting up to six weeks for surgery would not hurt these women, many women did not wish to wait and refused to participate in the study.

The authors concluded that further studies are needed, but the findings suggest that local topical medicine delivery to the breast may be effective and might lower side effect risk.

“Blocking the cancer-stimulating effects of estrogen has proven to be one of the most effective anticancer therapies in patients with estrogen-receptor positive breast cancer," explained Brian Lawenda, MD, national director of Integrative Oncology and Cancer Survivorship at 21st Century Oncology in Las Vegas. Tamoxifen is one of the more common medications for this use, he said, and is often use for the DCIS tumors.

“Unfortunately, tamoxifen is not without potential side effects, risks and complications, such as increased risk of blood clots, uterine cancer, hot flashes, weight gain, muscle and joint aches and others,” Dr. Lawenda told dailyRx News. He added that it is great to learn that the gel worked equally well to the oral form of the medication.

Dr. Lawenda said that he would like to see further research conducted on this topic.

"Although this is quite a reassuring finding to see similar anticancer activity between the two forms of the drug, what was truly exciting, although not surprising, was that the production of proteins involved in blood clotting and in tumor growth were significantly lower in the patients using the topical form of tamoxifen. This doesn’t prove that topical tamoxifen will lower the risk of blood clotting and tumor growth, [but] it is promising," he said.

"I'm hopeful that future studies will be conducted to further explore these issues," he said

The study results were published July 15 in Clinical Cancer Research.

The authors did not disclose any conflicts of interest.

Review Date: 
July 14, 2014
Last Updated:
July 15, 2014