No_intervention: Standard treatment

Patients in the control arm will be treated as usual after the first-line breast cancer treatment. Specifically, in Valencia, this process entails biannual medical evaluation control visits for the first port-treatment year at the Oncology Department, including standardised blood examinations.~On top of that, patients of this group will be offered 3 supportive consultation sessions, over the phone, with generic advice on desired lifestyle choices (physical activity, dietary habits, sleep habits and social mobility) that will be helpful for managing the ongoing treatment

Experimental: Standard treatment + REBECCA

Patients will be trained in the use of the complementary monitoring modules of the REBECCA mobile and online monitoring platform, which will be used longitudinally, facilitating the collection of real world data within the REBECCA framework. Their supervising health personnel will be given access to the REBECCA patient dashboard, that provides in-depth information about their lifestyle, as well as continuous REBECCA measurements for their online behaviour and self- or companion-reported measures of emotional state and quality of life.~Unlike those in the Standard care study-arm, 3 phone-based consultation sessions in the first 12 months of treatment visits will be scheduled based on system-predicted eminent life functionality and emotional state deteriorations (and potential decrease in treatment compliance), targeting the just-in-time patient support, aiming at improving treatment acceptance and efficacy