Adding Ibrance (chemical name: palbociclib) to Faslodex (chemical name: fulvestrant) as a first treatment for advanced-stage or metastatic hormone-receptor-positive, HER2-negative breast cancer improved progression-free survival compared to Faslodex alone, according to early results from the FLIPPER study.
The research was presented on Sept. 21, 2020, at the European Society for Medical Oncology Virtual Congress 2020. Read the abstract of ”GEICAM/2014-12 (FLIPPER) study: First analysis from a randomized phase II trial of fulvestrant (F)/palbociclib (P) versus (vs) F/placebo (PL) as first-line therapy in postmenopausal women with HR (hormone receptor)+/HER2- endocrine sensitive advanced breast cancer (ABC).”
Progression-free survival is how long a person lives without the cancer growing.
Metastatic breast cancer is breast cancer that has spread to parts of the body away from the breast, such as the bones or liver.
Doctors call cancer that is metastatic at first diagnosis de novo metastatic.
Endocrine-sensitive breast cancer is breast cancer that responds to hormonal therapy. In the FLIPPER study, some of the women had been diagnosed with early-stage hormone-receptor-positive, HER2-negative breast cancer that was successfully treated and then came back (recurred) as metastatic disease more than a year after the women finished 5 or more years of hormonal therapy. The rest of the women were diagnosed with de novo metastatic disease.
About Ibrance and Faslodex
Ibrance is a cyclin-dependent kinase (CDK) 4/6 inhibitor. A kinase is a type of protein in the body that helps control cell division. Ibrance works by stopping cancer cells from dividing and growing.
Ibrance is approved to treat women and men diagnosed with advanced-stage or metastatic hormone-receptor-positive, HER2-negative breast cancer in combination with:
- an aromatase inhibitor as the first hormonal therapy treatment
- Faslodex if the cancer has grown after being treated with hormonal therapy
Ibrance is a pill taken by mouth.
Faslodex is a type of hormonal therapy called an estrogen receptor downregulator (ERD). ERDs block the effect 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.
The FLIPPER study
Right now, the combination of Ibrance and Faslodex is approved as a second-line treatment for advanced-stage or metastatic disease, after the cancer has grown while being treated with hormonal therapy. The FLIPPER study wanted to see if Ibrance and Faslodex could be a better first treatment than Faslodex alone for advanced-stage or metastatic hormone-receptor-positive, HER2-negative breast cancer.
The study included 189 postmenopausal women diagnosed with either:
- advanced-stage or metastatic hormone-receptor-positive, HER2-negative breast cancer that was a recurrence of early-stage disease more than 1 year after finishing 5 or more years of hormonal therapy
- de novo metastatic hormone-receptor-positive, HER2-negative disease
About 45.5% of the women were diagnosed de novo metastatic.
The women joined the study between February 2016 and January 2019. About half were older than 64, and half were younger.
None of the women had been treated for advanced-stage or metastatic breast cancer.
The women were randomly assigned to one of two treatments:
- Ibrance and Faslodex (94 women)
- placebo, a pill that looked just like Ibrance but contained no medicine, and Faslodex (95 women)
After about 2.5 years of follow-up, progression-free survival was:
- 31.8 months for women treated with Ibrance and Faslodex
- 22 months for women treated with Faslodex alone
This difference was statistically significant, which means that it was likely due to the difference in treatment and not just because of chance.
The researchers also looked to see if progression-free survival was different in women diagnosed with recurrent metastatic disease compared to women diagnosed with de novo metastatic disease.
For women diagnosed with recurrent metastatic disease, progression-free survival was:
- 30.5 months for women treated with Ibrance and Faslodex
- 27.3 months for women treated with Faslodex alone
For women diagnosed with de novo metastatic disease, progression-free survival was:
- 33.4 months for women treated with Ibrance and Faslodex
- 16.4 months for women treated with Faslodex alone
This difference also was statistically significant.
Additionally, more women treated with Ibrance and Faslodex showed some response to the treatment. Treatment response rates were:
- 68.3% for women treated with Ibrance and Faslodex
- 42.2% for women treated with Faslodex alone
“These data provide evidence for superiority of fulvestrant plus palbociclib versus fulvestrant plus placebo in the first-line treatment of [patients with] endocrine-sensitive disease,” said Joan Albanell, M.D., during his presentation of the study.
“In this trial, they were able to demonstrate a significant progression-free survival [improvement] that was particularly important in those patients that had de novo metastatic breast cancer,” Michael Method, M.D., oncologist and senior medical adviser and global lead for adjuvant breast cancer treatment research at Lilly Oncology, told Breastcancer.org. “And while this was only a phase II clinical trial, it adds to the body of evidence confirming the benefits of using this class of drugs … in those patients with hormone-receptor-positive, HER2-negative breast cancer.”
Ibrance side effects
Like almost all cancer medicines, Ibrance can cause side effects, some of them severe.
In the FLIPPER study:
- 89.4% of women treated with Ibrance and Faslodex experienced at least one side effect
- 62.1% of women treated with Faslodex alone experienced at least one side effect
Overall, 15% of women treated with Ibrance and Faslodex and 4.3% of women treated with Faslodex alone stopped treatment because of side effects.
For women treated with Ibrance and Faslodex, the most common side effects were:
- low white blood cell counts
- low red blood cell counts
What this means for you
If you’ve been diagnosed with advanced-stage or metastatic hormone-receptor-positive, HER2-negative breast cancer, the results from the FLIPPER study are very encouraging. Still, these are early results. More research is needed to see if this improvement in progression-free survival translates into better overall survival — how long a person lives, whether or not the cancer grows.
Right now, the combination of Ibrance and Faslodex is not approved as a first treatment for advanced-stage or metastatic hormone-receptor-positive, HER2-negative breast cancer. Still, if you’ve been diagnosed with this type of disease — especially if you were diagnosed de novo metastatic — and are deciding on first treatments with your doctor, you may want to bring up this study and ask if there are any clinical trials using Ibrance and Faslodex as a first treatment that might be a good fit for you and your unique situation.
For more information on CDK4/6 inhibitors, visit the Breastcancer.org Targeted Therapy pages.
To discuss treatment options with others being treated for advanced disease, join the Breastcancer.org Discussion Board forum Stage IV and Metastatic Breast Cancer ONLY.
Written by: Jamie DePolo, senior editor
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