Kisqali (ribociclib), an oral treatment currently used to treat advanced breast cancer, may also reduce the odds of tumors coming back in patients with earlier-stage disease, a new study suggests.
The investigation included more than 5,000 early-stage breast cancer patients with what’s known as hormone receptor–positive (HR-positive), HER2-negative tumors, the most common subtype. This kind of breast cancer is typically treated with surgery, chemotherapy, or radiation followed by several years of endocrine therapy to prevent tumors from coming back.
All the patients in the study received this standard regimen, with five years of endocrine therapy after initial treatments. Scientists randomly assigned half of the patients to start three years of treatment with the targeted cancer drug Kisqali when they began endocrine therapy.
Adding Kisqali to the follow-up treatment protocol reduced the overall risk of breast cancer recurrence by 25 percent, according to findings presented at the annual meeting of the American Society of Clinical Oncology (ASCO).
Study Results Are Good News, but Questions Remain
“These results tell us that ribociclib can help prevent some very early recurrences in the most aggressive HR-positive breast cancers, and that’s good news for patients,” says Angela DeMichele, MD, a professor and coleader of the breast cancer program at the Abramson Cancer Center at the University of Pennsylvania in Philadelphia.
“Whether this will ultimately continue to benefit patients over the long run remains to be seen,” cautions Dr. DeMichele, who wasn’t involved in the research.
One drawback of the current study is that it focused only on whether Kisqali could stall tumor growth and prevent cancer recurrence, not whether the drug might help people live longer or prevent cancer deaths.
“Based on these early results, it appears that the addition of three years of ribociclib to endocrine therapy can significantly reduce recurrence, which could in turn improve survival,” says Rita Nanda, MD, the director of breast oncology at the University of Chicago Medicine, who wasn’t involved in the study.
“We need longer follow-up to determine if this is in fact the case,” she adds.
What Is Kisqali (Ribociclib)?
Kisqali is in a family of medicines known as cyclin dependent kinase (CDK) inhibitors. Kinase is a protein that plays a role in cell growth and division; blocking it helps stop cancer cells from growing and spreading.
Kisqali was first approved by the FDA in 2017 for metastatic HR-positive, HER2-negative breast cancer. A year later it was cleared for additional patients with advanced breast cancer.
Previous trials testing other CDK inhibitors for follow-up therapy in early-stage breast cancer have had mixed results, and Kisqali is not yet FDA-approved to treat patients with these tumors.
One study published earlier this year in the Lancet Oncology found that adding the CDK inhibitor Verzenio (abemaciclib) endocrine therapy for early-stage HR-positive, HER2-negative breast cancer significantly reduced the chances of cancer coming back over four years of follow-up.
But a study published in the Lancet Oncology in February 2021 found that adding the CDK inhibitor Ibrance (palbociclib) to endocrine therapy for early-stage HR-positive, HER2-negative breast cancer didn’t make a difference in cancer recurrence rates.
At this point, none of the CDK inhibitors are FDA-approved to treat these early-stage tumors. Novartis, the drugmaker that sells Kisqali and funded the new study of the drug in early-stage breast cancer, said in a statement that it plans to seek FDA-approval for this patient population by the end of 2023.
Why Do We Need New Treatments for Early-Stage HR-Positive, HER2-Negative Breast Cancer?
HR-positive, HER2-negative breast cancer is the most common subtype of the disease, making up nearly 70 percent of all breast cancer cases in the United States, according to ASCO.
Right now, there aren’t good targeted treatment options for most patients with early-stage HR-positive, HER2-negative breast cancer, said the lead Kisqali study author Dennis Slamon, MD, PhD, the director of women’s cancer research at the University of California in Los Angeles Jonsson Comprehensive Cancer, in the ASCO statement.
“There is a significant unmet need for both reducing the risk of recurrence and providing a tolerable treatment option that keeps patients cancer-free without disrupting their daily life,” Dr. Slamon said.
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