The CDK4/6 inhibitor Kisqali (chemical name: ribociclib) in combination with the hormonal therapy Faslodex (chemical name: fulvestrant) offered better overall survival than Faslodex alone in postmenopausal women diagnosed with advanced-stage, hormone-receptor-positive, HER2-negative breast cancer that either hadn't been treated yet or had been treated with only one hormonal therapy, according to the latest results from the MONALEESA-3 study.
The research was presented on Sept. 29, 2019, at the European Society for Medical Oncology (ESMO) 2019 Congress. Read an ESMO media release about the study and the presentation abstract.
Advanced-stage breast cancer is either locally advanced breast cancer or metastatic breast cancer. Locally advanced breast cancer is breast cancer that has spread to tissue near the breast, but not to parts of the body away from the breast. Metastatic breast cancer is cancer that has spread to parts of the body away from the breast, such as the bones or liver. Overall survival is how long a person lives, whether or not the cancer grows.
About Kisqali and Faslodex
Kisqali is a cyclin-dependent kinase 4/6 (CDK4/6) inhibitor. A kinase is a type of protein in the body that helps control cell division. Kisqali works by stopping cancer cells from dividing and growing. Kisqali is a pill taken by mouth.
Kisqali is used in combination with an aromatase inhibitor to treat advanced-stage or metastatic, hormone-receptor-positive, HER2-negative breast cancer that hasn’t been treated with hormonal therapy yet in premenopausal, perimenopausal, and postmenopausal women. Arimidex (chemical name: anastrozole), Aromasin (chemical name: exemestane), and Femara (chemical name: letrozole) are aromatase inhibitors. Premenopausal and perimenopausal women treated with Kisqali also should be treated with a luteinizing hormone-releasing hormone agonist, such as Zoladex (chemical name: goserelin), to suppress ovarian function.
Kisqali also is used in combination with the hormonal therapy Faslodex to treat advanced-stage or metastatic, hormone-receptor-positive, HER2-negative breast cancer that hasn’t been treated with hormonal therapy yet or has grown while being treated with a different hormonal therapy in postmenopausal women.
You take Kisqali on a 28-day cycle:
- for 21 days, you take Kisqali at the same time each day, with or without food
- then for 7 days, you don't take Kisqali
Faslodex is a type of hormonal therapy called an estrogen receptor downregulator (ERD). ERDs block the effects of estrogen in breast tissue. ERDs sit in the estrogen receptors in breast cells. If an ERD is in the estrogen receptor, there is no room for estrogen and it can't attach to the cell. If estrogen isn't attached to a breast cell, the cell doesn't receive estrogen's signals to grow and multiply. ERDs also:
- reduce the number of estrogen receptors
- change the shape of breast cell estrogen receptors so they don't work as well
Faslodex is used:
- alone as the first treatment for postmenopausal women diagnosed with hormone-receptor-positive, HER2-negative, advanced-stage breast cancer that hasn’t been treated with hormonal therapy
- to treat postmenopausal women diagnosed with metastatic, hormone-receptor-positive breast cancer that has stopped responding to other hormonal therapy medicines, such as tamoxifen
Faslodex is given as an injection into a muscle, usually once a month.
About the MONALEESA-3 study
In the MONALEESA-3 study, the researchers randomly assigned 726 postmenopausal women diagnosed with advanced-stage, hormone-receptor-positive, HER2-negative breast cancer to one of two treatments:
- Kisqali plus Faslodex (484 women)
- Faslodex plus placebo (a dummy pill that looked just like Kisqali) (242 women)
Although men were eligible to enroll in the study, because of the quick recruitment time, no men ended up being part of the study.
The women had either never been treated for advanced-stage breast cancer or had been treated with just one type of hormonal therapy for advanced-stage disease.
Results from the study published in 2018 showed that adding Kisqali to Faslodex improved progression-free survival by about 8 months compared to Faslodex alone. Progression-free survival was:
- 20.5 months for women treated with Kisqali and Faslodex
- 12.8 months for women treated with Faslodex alone
Progression-free survival is how long a person lives without the cancer growing.
Latest MONALEESA-3 results
Besides progression-free survival, the researchers also wanted to know if Kisqali could improve overall survival.
The cut-off date for overall survival data analysis was June 3, 2019. At that time, 153 women were still being treated as part of the study:
- 121 women in the Kisqali and Faslodex group
- 32 women in the Faslodex alone group
At that time, 275 women had died:
- 167 women treated with Kisqali and Faslodex (34.5%)
- 108 women treated with Faslodex alone (44.6%)
This difference was statistically significant, which means that it was likely because of the difference in treatment and not just due to chance.
"This is a significant, practice-changing report, in that we are now saying that patients with advanced breast cancer will have an overall survival benefit if they get the CDK4/6 inhibitor ribociclib upfront at the time of their recurrence, even if they have not had any prior endocrine therapy at the time of presenting with metastatic disease," said Slamon at a media briefing about the study.
"The argument has always been by some experts that you should first treat with endocrine therapy alone and then if patients recur, you would add something like a CDK4/6 inhibitor," he continued. "In other words, you get what you can out of endocrine therapy alone — and save a CDK4/6 inhibitor until the subsequent recurrence. The data from MONALEESA-3 clearly show that if postmenopausal patients receive this right up front there is a very significant benefit — not only in progression-free survival, which had already been published — but now with this new report in overall survival — which is the hardest endpoint to reach, and the most important one in terms of making an impact on the disease."
What this means for you
The latest results from MONALEESA-3 are extremely promising. If you're a postmenopausal woman who has been diagnosed with advanced-stage, hormone-receptor-positive, HER2-negative breast cancer and are deciding on first treatments for the advanced-stage disease, you may want to talk to your doctor about this study.
The results strongly suggest that Kisqali and Faslodex is a better first treatment for this type of breast cancer than hormonal therapy alone. While this is not the standard of care, Slamon believes it will be soon.
For more information on Kisqali and other CDK4/6 inhibitors, visit the Breastcancer.org Targeted Therapies pages.
Written by: Jamie DePolo, senior editor
Reviewed by: Brian Wojciechowski, M.D., medical adviser