Topical version of breast cancer drug could reduce side effects, risk factor

Local researchers hope to make an effective and widely-used breast cancer drug even better for patients with a topical version that not only stops the spread of disease, but also may help reduce a major risk factor.

It goes on just like hand sanitizer or body lotion, but the gel’s purpose goes far deeper than skin. It’s an alternative form of tamoxifen, an oral drug known to help stop the spread of cancer cells. Commonly prescribed for patients with ductal carcinoma in situ (DCIS), or cancer contained in the milk ducts of the breast, it’s often recommended as a prevention therapy for healthy women at high risk to develop breast cancer in the future.

“This is a full dose of the gel, and then the woman just applies it on the breast starting from the inside to the outside,” said breast cancer researcher Dr. Seema Khan, Northwestern Medicine.

Dr. Khan and her team have been working on the alternative form for years. We first reported their findings in 2014, when the gel was shown to be as effective as the oral version of tamoxifen. Dr. Khan said many women who have DCIS or are healthy but at increased risk often don’t want to take tamoxifen by mouth because of a chance of unpleasant side effects, which can range from hot flashes to rare but more serious medical problems like uterine cancer and blood clots.

With the drug concentrated in the breast, and far less circulating in the blood as it does with an oral medication, patients could experience fewer side effects.

“This was very encouraging because it told us the effect on the breast was good, the concentration of the drug in the breast was good and very little was in the circulation,” Dr. Khan said.

But further study of the promising alternative was halted early when the gel’s maker pulled funding. Four years later, Dr Khan is back at it, testing it out in multiple studies including one that will help determine if it reduces another known risk factor: breast density.

“Women who have dense breast tissue on mammography are known to be at higher risk for breast cancer, but also the dense breast tissue interferes with the abilities of mammograms to see abnormalities in the breast," Dr. Khan said.

Doctors at Northwestern are currently enrolling patients for both studies. the anti-cancer gel trials and studies to reduce breast density. Patients can apply to participate in trials of the anti-cancer gel, or in either one of two breast density trials.

"Cancer prevention is a very complicated area, but there are many people working on it now. The whole field is gathering momentum, and we are hoping that this work with transdermal delivery, through the skin, of a cancer prevention agent will add to that momentum,” Dr. Khan said.

For more information, contact study coordinator Yanfei Xu at (312) 472-0585 or yanfei-xu@northwestern.edu.