Evaluating the long-term effectiveness of adding ribociclib to hormone therapy in younger patients with HR+/HER2- advanced breast cancer.

This study evaluated the long-term effectiveness of adding ribociclib (Kisqali) to endocrine (hormone) therapy in pre-/perimenopausal patients with hormone receptor-positive (HR+)/HER2-negative (HER2-) advanced breast cancer (BC). The data showed that adding ribociclib to hormone therapy significantly improved survival outcomes than hormone therapy alone over the long-term in these patients.

BC is classified into different subtypes depending on the presence or absence of certain receptors (proteins found on the surface of the cancer cells). HR+ and HER2- BC tests positive for the estrogen and/or progesterone receptor (female sex hormones) and negative for the HER2 protein. This type of cancer accounts for 70% of all BCs. Patients with this subtype of BC commonly receive hormone therapy which acts by decreasing the female hormones.

Ribociclib is a targeted therapy. It blocks CDK4 and CDK6 which are important in regulating the cell cycle and cell growth. Blocking these proteins has been shown to slow the growth of HR+ BC. Ribociclib plus endocrine therapy significantly improved survival outcomes in younger women (who have not yet reached menopause) with HR+/HER2- advanced BC. However, the long-term effectiveness of adding ribociclib to hormone therapy in these patients is still unknown.

This study involved 672 pre-/perimenopausal women with HR+/HER2- advanced BC. Patients were randomly assigned into 2 groups. Group 1 included 335 patients who received ribociclib plus hormonal therapy. Group 2 included 337 who received a placebo plus hormonal therapy. The average follow-up time was 53.5 months.

The average overall survival for group 1 was 58.7 months compared to 48 months for group 2. Patients in group 1 were 24% more likely to have a better survival than patients in group 2. After 48 months, 60% of patients in group 1 were alive compared to 50% of patients in group 2.

The average survival without cancer worsening for group 1 was 44.2 months compared to 31 months for group 2. Patients in group 1 were 32% more likely to survive without cancer worsening than patients in group 2.

The time to first chemotherapy was significantly delayed with ribociclib versus placebo. The most common side effects associated with ribociclib were decreased white blood cells and liver damage.

This study concluded that adding ribociclib to hormone therapy significantly improved survival outcomes than hormone therapy alone over the long-term in younger patients with HR+/HER2– advanced BC.

The study was sponsored by Novartis and Astex Pharmaceuticals, the manufacturers of ribociclib.