After a reassessment of new data cut-offs of the advantages and disadvantages of ribociclib, researchers have found that an added benefit is not proven for initial endocrine therapy with ribociclib in combination with the aromatase inhibitor letrozole and for subsequent endocrine therapy with ribociclib plus fulvestrant in patients post menopause, with hormone receptor-positive, human epidermal growth factor receptor 2-negative, locally advanced or metastatic breast cancer.

The first assessment of ribociclib was conducted in 2017 by the German Institute for Quality and Efficiency in Health Care (IQWiG), which found that the drug in combination with an aromatase inhibitor to have lesser benefit than the comparator therapy due to semi-severe adverse effects (AEs). In the second assessment conducted in 2019, the survival advantage for the combination with fulvestrant shown in the ongoing MONALEESA-3 was outweighed by the AEs, according to the IQWiG.

In the new data cut-offs from both studies, the survival advantages for the combination with fulvestrant and combination with an aromatase inhibitor were shown, but major disadvantages were also evident, according to the IQWiG. Women treated with ribociclib developed severe AEs much more frequently than study participants in the comparator arms of the studies, specifically severe neutropenia, according to the study authors.

The researchers noted that in women who have already received endocrine therapy for the advanced stage, there was no statistically significant advantage in overall survival (OS) under ribociclib plus fulvestrant. Further, the major positive effect for emotional functioning in the outcome category “health-related quality of life” for patients aged 65 years and older did not have greater weight in the assessment than the most severe AEs of considerable or major extent.

In addition, both positive and negative effects were shown for the combination of ribociclib and the aromatase inhibitor letrozole in comparison with placebo and letrozole. Advantages in OS and future perspective and the disadvantages in severe AEs balanced, with an added benefit not proven in this scenario, according to the study authors.

Ribociclib in breast cancer: added benefit for certain women after menopause. IQWIG. Published June 2, 2020. Accessed June 8, 2020.