Feasibility of an N-of-1 trial using a crossover design to evaluate music therapy in patients with breast cancer undergoing adjuvant chemotherapy: a multicentre pilot study protocol in two Italian centres (IMPACT-CASTA DIVA).

INTRODUCTION: Breast cancer is often accompanied by significant psychological and physical symptoms during chemotherapy, which have a considerable impact on quality of life. Music therapy is a non-pharmacological intervention that can support psychological well-being but the way individuals respond to the treatment can vary considerably. Traditional group-based studies do not allow such variability to be captured. N-of-1 trials, which are based on repeated intra-individual comparisons, offer an innovative way to assess personalised effects. This pilot study aims to evaluate the feasibility of this approach in patients with breast cancer. METHODS AND ANALYSIS: This multicentre pilot study uses an N-of-1 design combined with a crossover design involving 24 patients with breast cancer who are undergoing adjuvant chemotherapy. Participants will be randomised into alternating sequences of phases with and without music therapy each lasting 4 weeks. The intervention consists of weekly 60-minute group sessions incorporating receptive and active techniques as well as personalised playlists. The primary outcomes focus on feasibility, including dropout rate and missing data as well as acceptability. The secondary outcomes include measures of psychological and physical well-being as assessed using validated instruments (State-Trait Anxiety Inventory, Self-Rating Depression Scale, Quality of Life, Emotion Thermometers, Visual Analogue Scale and Pittsburgh Sleep Quality Index). The analysis will be primarily descriptive, exploring individual trajectories and intra- and inter-patient variability using mixed-effects models. ETHICS AND DISSEMINATION: The study protocol was approved by the Research Ethics Committee of AOU Maggiore della Carità Novara (Protocol No. 590/CE/2025) and the Research Ethics Committee of Palermo 2 (Protocol No. 137/2025) and will be conducted in accordance with the principles of the Declaration of Helsinki. Written informed consent will be obtained from all participants. The results will be disseminated through peer-reviewed scientific publications and presentations at national and international scientific conferences. TRIAL REGISTRATION NUMBER: NCT07549685.