Can topical skin gel shrink some breast cancer tumours?

Can a gel applied to the skin of a woman's breast provide the same cancer-fighting benefits as a pill taken by mouth but reduce the side effects of the medicine?

Northwestern Medicine researchers are conducting a clinical trial to see if a gel containing an active form of tamoxifen, an anti-estrogen therapy, can provide the drug's benefits with decreased risk of adverse health effects compared to those who take the oral tamoxifen.

The new study drug is being tested on participants recently diagnosed with the earliest form of non-invasive breast cancer. Women who are treated for this kind of cancer (called ductal carcinoma in situ or DCIS) are usually advised to take oral tamoxifen for five years if their DCIS is hormone sensitive. In this research study, half the women receive the study gel and half the women receive the oral tamoxifen.

Tamoxifen, when taken as a pill for five years, reduces the risk of cancer recurrence in the same spot by a third and prevents the occurrence of half of new breast cancers. The therapy, however, has an increased risk of blood clots, uterine cancer and hot flashes. As a result, many women decline the treatment.

''The gel is a way to minimise exposure to the rest of the body and concentrate the drug in the breast where it is needed," said principal investigator Seema Khan, M.D., co-leader of the breast cancer program at the Robert H. Lurie Comprehensive Cancer Center of Northwestern University and a surgical oncologist at Northwestern Memorial Hospital. "Delivery of the drug through the skin of the breast means there will be very little drug circulating through the bloodstream and the body. This should reduce the possibility of blood clots."

Khan compared it to the current practice of delivering estrogen via a skin patch to avoid the risk of blood clots. And because the circulating levels of the topical drug are very low, the gel should be unlikely to cause other side effects such as hot flashes and the increased risk of uterine cancer.