The eHealtHeart Mobile Application for Managing Cardiac Toxicity in Patients with Breast Cancer: Preliminary Results From the CARDIOCARE Multicenter Study (Preprint)

<sec> <title>BACKGROUND</title> Breast cancer treatments can cause cardiotoxicity, particularly among elderly patients with comorbidities and frailty. This dual burden poses complex clinical challenges, including increased risk of cardiac complications, reduced resilience, and reduced quality of life. To address these issues effectively, there is a growing need for continuous, patient-centered monitoring and integrated psycho-emotional support that goes beyond conventional care, empowering patients and enabling proactive, personalized interventions. </sec> <sec> <title>OBJECTIVE</title> This study aimed to design, develop and evaluate a mobile application, the eHealtHeart, intended to support elderly women with breast cancer by enabling continuous cardiovascular monitoring and providing behavioral and psycho-emotional interventions. </sec> <sec> <title>METHODS</title> The eHealtHeart mobile application was developed through a user-centered, multi-phase process involving active input from elderly patients and healthcare professionals. The application integrates physiological data collected via a smartwatch and a chest-strap (which monitors heart rate and heart rate variability) into 6 interactive digital modules addressing: (i) mobility &amp; vitality, (ii) psychology &amp; wellbeing, (iii) cognitive stimulation, (iv) education, (v) geriatric assessments and (vi) smart recommendations. A total of 79 women (mean age 67 ± 7 years) used the eHealtHeart mobile application over a six-month period, after which they completed three evaluation instruments: (1) the System Usability Scale (SUS), (2) a Technology-Acceptance-Model (TAM) questionnaire assessing Perceived Usefulness [PU], Perceived Ease-of-Use [PEU], Intention-to-Use [IU], Attitude-toward-Use [ATU]), and (3) a custom survey evaluating functionality, reliability and data security. </sec> <sec> <title>RESULTS</title> The mean SUS score was 69.05 ± 15.84, with 61 out of 79 participants (77%) scoring above the established 68-point benchmark for good usability. TAM results were favorable across all constructs: Perceived Usefulness (PU) = 3.72 ± 0.92; Perceived Ease of Use (PEU) = 3.35 ± 1.05; Intention to Use (IU) = 3.35 ± 1.05; and Attitude Toward Use (ATU) = 3.84 ± 0.83, all rated on a 1–5 Likert scale. Functionality was rated highest for ease of use (3.96 ± 0.92) and system performance (3.21 ± 0.71); while reliability accuracy was also strong (3.94 ± 0.98), indicating no major technical limitations. Participants reported high perceived data security (4.26 ± 0.94). Digital literacy was strongly associated with usability, with a significant correlation between SUS scores and the Digital Literacy Index (r = 0.78, p &lt; 0.001). Open-ended user feedback highlighted the value of biofeedback features, cognitive training games and personalized recommendations, although some users reported occasional data synchronization delays. These findings represent an interim analysis of 79 participants who completed the intervention while the CARDIOCARE randomized controlled trial is still ongoing. </sec> <sec> <title>CONCLUSIONS</title> The eHealtHeart mobile application demonstrated good usability and high levels of acceptance among breast cancer patients at risk of cardiotoxicity, including those with limited digital literacy. Its user-centered design, integrating cardiovascular monitoring with behavioral and psycho-emotional interventions offers a novel approach to addressing the complex care needs in geriatric oncology. These interim findings support the feasibility and acceptability of the proposed intervention and highlight its potential for broader implementation in routine care. Future iterations may incorporate artificial intelligence to enable personalized, adaptive support and further enhance clinical impact. </sec> <sec> <title>CLINICALTRIAL</title> ClinicalTrials.gov NCT06334445 </sec>