The risk of death was cut by nearly a third compared with those treated with hormone therapy alone, according to the study presented at the American Society of Clinical Oncology's annual meeting in Chicago.
The mortality rate was 29 per cent less than when patients, all under 59 and pre-menopausal, were randomly assigned a placebo.
This study focused on a particular type of breast cancer which is fueled by the hormone estrogen and which is the cause for two-thirds of total cases among younger women.
After 42 months, 70% of those treated with the combination therapy were still alive, compared with 46% of those who received just hormone therapy.
She passed the following statement: "you can actually achieve synergy by the addition of these cell-cycle inhibitors on top of the therapy of blocking of the hormone".
The drug operates by restricting the activity of cancer-cell promoting enzymes.
The treatment is way less toxic than the typical chemotherapy because it targets the cancerous cells more selectively, makes their ability of multiplication block. About 41,000 women and 450 men die each year from breast cancer, according to the US Centers for Disease Control and Prevention.
Ribociclib and hormone therapy have been used to treat postmenopausal women with breast cancer previously and last year the combination therapy was approved by the US Food and Drug Administration for use in premenopausal women. (Most breast cancers fall into this category.) But a year ago, the FDA extended the approval to include younger, premenopausal women, as well.
In addition, patients who develop breast cancer early tend to have more complex cases.
In the study participated women who haven't enter menopause and who have advanced breast cancer.
Even though the patients had advanced disease, the drug stalled the disease for an average of eight months.
The researchers noted: "The study was conducted among 672 women under 59 who received ribociclib, in combination with a common hormone therapy".
Named ribociclib and manufactured by Novartis under the Kisqali brand, which is taken in pill form, costs over $12,000 or N4.32 million monthly, according to the prescription pricing website GoodRx. "The use of ribociclib as a frontline therapy significantly prolonged overall survival, which is good news for women with this bad disease".
"Hopefully, these data will enable access for this product for more women around the world, particularly in healthcare systems which assess value rigorously as part of their decisions for national access to drugs", Burstein added. A new global clinical trial is now underway.