San Antonio, Tex. — A new drug cocktail might be the right mix to fight breast cancer after it becomes resistant to standard therapy. Details of a new study supporting this approach suggest it's possible to re-sensitize tumors thus allowing treatments to work again. The findings were presented today at the CTRC-AACR San Antonio Breast Cancer Symposium.
The study involves post-menopausal women whose advanced breast cancers are fueled by estrogen, often called estrogen-receptor or progesterone-receptor positive cancers. The standard treatment is anti-hormonal medicines, such as aromatase inhibitors (AIs), which lower the amount of estrogen in the body. Over time, however, the cancer figures out a way to thrive without the estrogen. The treatment strategy under investigation to fight this resistance combines an aromatase inhibitor with sorafenib, an oral medication FDA-approved to treat liver and kidney cancers.
"We believe the sorafenib might disrupt the machinery created by the tumor to grow without the estrogen," says Claudine Isaacs, MD, clinical director of breast cancer program at Georgetown Lombardi Comprehensive Cancer Center and presenting author of the study. "After the machinery is destroyed, the aromotase inhibitor can do its work again. We're already seeing some encouraging responses to this approach."
The multi-center, phase II study involves 35 post-menopausal women with metastatic breast cancer resistant to aromotase inhibitors. The women continue taking an aromotase inhibitor for the study, but they also take sorafenib. The analysis presented today demonstrates a clinical benefit rate in 20 percent of the women. Clinical benefit means the patient has a complete or partial response and includes those who have stable disease for at least 6 months (24 weeks).
Isaacs says this finding suggests that sorafenib is acting to reverse resistance to AIs as this type of response would not have been expected with either sorafenib alone or with continuing the AI.
"To manage breast cancer long term, it's apparent that we may need to continually switch drugs to keep up with how a cancer evolves and evades each approach," Isaacs concludes.
Isaacs says side-effects were common but most were mild or were managed by reducing the dose. Such side effects included redness and irritation of the palms and soles, skin rash, fatigue, nausea/vomiting and diarrhea. Serious hypertension occurred in about 11 percent of the patients. Isaacs says this factor was more easily managed if blood pressure was brought under good control before patients were administered the combination.
This study was funded by the Avon Patient for Progress Award and supported in part by Bayer. Isaacs is part of a speaker's bureau for Pfizer, the maker of Exemestane, an aromatase inhibitor. She is also on speaker's bureau for Abraxis Oncology, Genentech, GlaxoSmithKline, and Novartis.
About Lombardi Comprehensive Cancer Center
The Lombardi Comprehensive Cancer Center, part of Georgetown University Medical Center and Georgetown University Hospital, seeks to improve the diagnosis, treatment, and prevention of cancer through innovative basic and clinical research, patient care, community education and outreach, and the training of cancer specialists of the future. Lombardi is one of only 40 comprehensive cancer centers in the nation, as designated by the National Cancer Institute, and the only one in the Washington, DC, area. For more information, go to http://lombardi.georgetown.edu.
About Georgetown University Medical Center
Georgetown University Medical Center is an internationally recognized academic medical center with a three-part mission of research, teaching and patient care (through Georgetown's affiliation with MedStar Health). GUMC's mission is carried out with a strong emphasis on public service and a dedication to the Catholic, Jesuit principle of cura personalis – or "care of the whole person." The Medical Center includes the School of Medicine and the School of Nursing and Health Studies, both nationally ranked, the world-renowned Lombardi Comprehensive Cancer Center and the Biomedical Graduate Research Organization (BGRO), home to 60 percent of the university's sponsored research funding.