A study has found that the experimental targeted therapy medicine abemaciclib in combination with the hormonal therapy Faslodex (chemical name: fulvestrant) offered better progression-free survival than Faslodex alone in women diagnosed with metastatic, hormone-receptor-positive, HER2-negative breast cancer.
Progression-free survival is how long the women lived without the breast cancer growing.
The research was presented on June 3, 2017 at the 2017 American Society of Clinical Oncology (ASCO) Annual Meeting and published online on the same day by the Journal of Clinical Oncology:
- Read the ASCO annual meeting presentation abstract of "MONARCH 2: Abemaciclib in combination with fulvestrant in patients with HR+/HER2- advanced breast cancer who progressed on endocrine therapy"
- Read the Journal of Clinical Oncology abstract of "MONARCH 2: Abemaciclib in Combination With Fulvestrant in Women With HR+/HER2- Advanced Breast Cancer Who Had Progressed While Receiving Endocrine Therapy"
George Sledge, M.D., professor of oncology at Stanford University and member of the Breastcancer.org Professional Advisory Board, is the lead author of the study and presented the results at the ASCO annual meeting.
Like Ibrance (chemical name: palbociclib) and Kisqali (chemical name: ribociclib), abemaciclib is a cyclin-dependent 4/6 kinase inhibitor. A kinase is a type of protein in the body that helps control cell division. Abemaciclib works by stopping cancer cells from dividing and growing. Abemaciclib is a pill taken by mouth.
Metastatic breast cancer is breast cancer that has spread to a part of the body away from the breast, such as the bones or liver.
Hormonal therapy is used to treat hormone-receptor-positive breast cancer. Faslodex is an estrogen receptor downregulator. It blocks the effects of estrogen in breast tissue. Faslodex is a liquid that is given once a month as an injection into a muscle, usually at your doctor’s office.
In the MONARCH 2 study, researchers randomly assigned 669 women diagnosed with metastatic, hormone-receptor-positive, HER2-negative breast cancer that had grown while being treated with a hormonal therapy medicine other than Faslodex to one of two treatments:
- Faslodex plus placebo (a dummy pill that looked just like abemaciclib) (223 women)
- Faslodex plus abemaciclib (446 women)
None of the women had been treated with chemotherapy for metastatic breast cancer, and the women had been treated previously with only one hormonal therapy medicine.
Progression-free survival was 7 months longer in women treated with Faslodex plus abemaciclib compared to women treated only with Faslodex. Progression-free survival was:
- 9.3 months for women treated with Faslodex alone
- 16.4 months for women treated with Faslodex plus abemaciclib
This difference was statistically significant, which means that it was likely due to the difference in treatments and not just because of chance.
Most of the women in the study had some degree of tumor shrinkage with the combination of abemaciclib and Faslodex, said Dr. Sledge.
"Abemaciclib plus fulvestrant was an effective treatment for women with hormone-receptor-positive, HER2-negative advanced breast cancer whose disease progressed on prior endocrine therapy," said Sledge. "Abemaciclib dosed on a continuous schedule was generally well tolerated."
Like almost all cancer medicines, abemaciclib can cause side effects, some of them severe. Women in the abemaciclib-Faslodex treatment group were much more likely to have side effects than women in the Faslodex-alone treatment group. The most common side effects in the abemaciclib-Faslodex treatment group were:
- diarrhea: 86.4% of women in the abemaciclib group compared to 24.7% of women in the Faslodex alone group
- low white blood cell counts: 46.0% of women in the abemaciclib group compared to 4.0% of women in the Faslodex alone group
- nausea: 45.1% of women in the abemaciclib group compared to 22.9% of women in the Faslodex alone group
- fatigue: 39.9% of women in the abemaciclib group compared to 26.9% of women in the Faslodex alone group
If you’ve been diagnosed with metastatic, hormone-receptor-positive, HER2-negative breast cancer that has grown while being treated with hormonal therapy, you may want to talk to your doctor about this study. While abemaciclib is still an experimental medicine, Eli Lilly, the company that makes abemaciclib, has said that it plans to submit marketing applications for the medicine to the U.S. Food and Drug Administration (FDA) for breast cancer treatment later this year. Abemaciclib also is being studied to treat lung and pancreatic cancer.
Stayed tuned to Breastcancer.org for the latest information on abemaciclib and any FDA approvals for breast cancer treatment.