Ribociclib-endocrine Combination Therapy Versus Chemotherapy as 1st Line in Visceral mBC

Breast cancer is the most frequent malignancy in women and the leading cause of cancer mortality in most countries in Europe. Metastatic breast cancer remains an incurable disease with a median overall survival (OS) of 2-4 years and a 5-year survival of only 25%. Patients with hormone receptor (HR)-positive breast cancer involving visceral disease at diagnosis have an even worse outcome. Many oncologists still prefer to treat visceral disease primarily with chemotherapy rather than with endocrine treatment, thinking to receive a faster response with chemotherapy than with endocrine therapy, especially in patients with clinical symptoms or potentially threatening lesions. However, results from cross-sectional clinical practice studies suggest that endocrine therapy is associated with better quality of life, fewer concerns about side effects, less activity impairment and higher treatment satisfaction compared to chemotherapy. In addition, with the new data of CDK4/6 inhibitors combined with endocrine treatment there is an even better efficacy data available compared to endocrine therapy alone. The aim of this trial is to assess if patients treated with the combination of ribociclib and endocrine therapy respond to treatment as fast as patients treated with chemotherapy only, without decreasing their quality of life (QoL).