Which Cancer Survivors Need to Keep Blocking

Breast cancer survivors with biomarker benefit from extended endocrine therapy

(RxWiki News) Medications that block estrogen can be life savers for some breast cancer survivors. But does this approach help all breast cancer survivors?

New research revealed that a molecule showing the activity levels of two genes may help identify breast cancer survivors who will be helped with a second round of hormone therapy following five years of treatment with tamoxifen.

Tamoxifen is sold under several brand names - Nolvadex, Tamosin and Tamoxen. The medicine is prescribed to women whose breast cancer is driven by estrogen and known as estrogen receptor-positive (ER+).

This discovery could help women avoid breast cancer relapses without taking treatments that will not benefit them.

"Find out how long you should take a medication."

Researchers at Massachusetts General Hospital (MGH) Cancer Center conducted the study. Dennis Sgroi, MD, of the MGH Cancer Center and Department of Pathology was the lead author.

"Most patients with early stage, ER-positive breast cancer remain cancer-free after five years of tamoxifen treatment, but they remain at risk of recurrence for 15 years or longer after their initial treatment,” Dr. Sgroi said in a prepared statement.

A molecule known as a biomarker identifies patients who continue to be at risk after tamoxifen therapy and would benefit from additional therapy with the medication Femara (letrozole).

The ratio of two genes – HOXB13 and IL17BR – in women with ER+ breast cancer can be measured with a currently available test - the Breast Cancer Index from bioTheranostics.

For this study, investigators examined tissue samples from 83 patients whose breast cancer had returned and 166 breast cancer patients who did not have a recurrence.

The scientists found that women who had higher levels of HOXB13 than IL17BR were at high risk of cancer recurrence after being treated with tamoxifen. Those risks dropped significantly in at-risk patients who received letrozole.

“This is a very interesting result, and may indicate who needs an additional 5 years of endocrine therapy and who does not,” Adam Brufsky, MD, PhD, professor of medicine at the University of Pittsburgh, told dailyRx News.

“This discovery means that about 60 percent of women with the most common kind of breast cancer can be spared unnecessary treatment with the concomitant side effects and costs,” Paul E. Goss, MD, PhD, director of the Breast Cancer Research Program at the MGH Cancer Center and a co-author of the report, said in a press release. “But more importantly, the 40 percent of patients who are at risk of recurrence can now be identified as needing continued therapy with letrozole, and many will be spared death from breast cancer."

This research was published June 28 in the Journal of the National Cancer Institute.

This work was supported by grants from the Avon Foundation, the National Institute of Health, the Breast Cancer Foundation, the Department of Defense Breast Cancer Research Program, the NCI SPORE in breast cancer at Massachusetts General Hospital and Novartis, the maker of letrozole.

Drs. Sgroi and Erlander are named inventors on a patent to use the HOXB13/IL17BR assay to predict breast cancer outcome. Other authors disclosed financial ties with Novartis, Glaxo-Smith-Kline, Roche, Pfizer and Astrazeneca. Y. Zhang. Two authors are full-time employees and stockholders of bioTheranostics.

Review Date: 
June 28, 2013