BackgroundEfficacy and quality of life (QoL) are key criteria for therapy selection in metastatic breast cancer (MBC). In hormone receptor positive (HR +) human epidermal growth factor receptor 2 negative (HER2 −) MBC, addition of targeted oral agents such as everolimus or a cycline-dependent kinase 4/6 (CDK 4/6) inhibitor (e.g., palbociclib, ribociclib, abemaciclib) to endocrine therapy substantially prolongs progression-free survival and in the case of a CDK 4/6i also overall survival. However, the prerequisite is adherence to therapy over the entire course of treatment. However, particularly with new oral drugs, adherence presents a challenge to disease management. In this context, factors influencing adherence include maintaining patients’ satisfaction and early detection/management of side effects. New strategies for continuous support of oncological patients are needed. An eHealth-based platform can help to support therapy management and physician–patient interaction.MethodsPreCycle is a multicenter, randomized, phase IV trial in HR + HER2 − MBC. All patients (n= 960) receive the CDK 4/6 inhibitor palbociclib either in first (62.5%) or later line (37.5%) together with endocrine therapy (AI, fulvestrant) according to national guidelines. PreCycle evaluates and compares the time to deterioration (TTD) of QoL in patients supported by eHealth systems with substantially different functionality: CANKADO active vs. inform. CANKADO active is the fully functional CANKADO-based eHealth treatment support system. CANKADO inform is a CANKADO-based eHealth service with a personal login, documentation of daily drug intake, but no further functions. To evaluate QoL, the FACT-B questionnaire is completed at every visit. As little is known about relationships between behavior (e.g., adherence), genetic background, and drug efficacy, the trial includes both patient-reported outcome and biomarker screening for discovery of forecast models for adherence, symptoms, QoL, progression free survival (PFS), and overall survival (OS).DiscussionThe primary objective of PreCycle is to test the hypothesis of superiority for time to deterioration (TTD) in terms of DQoL = “Deterioration of quality of life” (FACT-G scale) in patients supported by an eHealth therapy management system (CANKADO active) versus in patients merely receiving eHealth-based information (CANKADO inform).EudraCT Number: 2016–004191-22