Adding ribociclib to endocrine therapy shows an improvement in invasive disease-free survival in HR+/HER2 BC patients

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Published: 3 Jun 2023
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Prof Dennis Slamon - UCLA, Los Angeles, USA

Prof Dennis Slamon speaks to ecancer about the phase III NATALEE trial of ribociclib and endocrine therapy as adjuvant treatment in patients with HR+/HER2− early breast cancer.

In this study, patients were randomised to receive either adjuvant ribociclib with hormonal therapy or hormonal therapy alone.

Prof Slamon says that the objective of this study was to decrease the recurrence rate without causing safety problems whilst maintaining the quality of life.

The study found that adding ribociclib to hormonal therapy showed a significant improvement in invasive disease-free survival for a broad population of people with HR-positive and HER2-negative early-stage breast cancer.

Prof Slamon says these results prove that ribociclib and endocrine therapy as adjuvant treatment can be a possible new treatment option for these patients.

Read more here.

Our study was a study of early breast cancer, in other words when patients are initially diagnosed, whether or not the addition of a CDK4/6 inhibitor, in particular ribociclib, added to the standard hormonal therapy that’s given to these patients, could improve outcomes. The objective was to decrease the recurrence rate without causing any problems with safety and maintaining quality of life.

What was the design of this study?

The study design was to evaluate some 5,101 patients who were randomised to receive the best available standard hormonal therapy, both premenopausal and postmenopausal women, versus that same therapy with the addition of this drug ribociclib, which is a CDK4/6 inhibitor that inhibits the cell cycle checkpoint. So that was the study design and the other part of the study design that was unique was that it enrolled a larger or a broader population of patients than had previously been enrolled in these early breast cancer studies.

What were the results of this study?

The results of the study showed that for the overall population the drug, when it was added, reduced the recurrence rate of the disease, it improved the disease free survival. It reduced the recurrence rate by 25%. It also reduced the incidence of distant disease free disease, meaning metastatic disease, by 26%. Those two numbers were statistically significant so the study was stopped prematurely because it had achieved efficacy so that we wouldn’t continue to randomise patients to a control arm if we had some evidence that there was something better.

How could this research impact the future treatment of breast cancer?

The exciting thing about these results is it indicates that this class of drugs, in particular this drug, ribociclib, can improve the outcomes for a broader population of patients than was previously thought. So normally we think of stage 2 disease or node negative disease as a lower risk or intermediate risk population because we know that patients with stage 2 disease still can have recurrences, about 30% of them will have recurrences as far out as two or three decades from their initial diagnosis. Patients with stage 3 disease, that can be up to over 50%. Can we improve and meet that unmet medical need to improve the outcomes of those patients? 

The study showed that this drug can do that and that’s what has been so exciting about it. The data will continue to mature further. Patients that are still waiting to complete their third year will continue on study. So we’ll look at additional looks at the data but it has already crossed the boundary for improving outcomes.