This study is a two-armed, single-blind, randomised controlled trial (RCT). Participants were selected from an oncology hospital affiliated with a university hospital in western Turkey between February and August 2023. Women who met the following criteria were included in the study: Women diagnosed with breast cancer who were undergoing chemotherapy, aged 18 years or older, voluntarily participating in the study, capable of communicating in Turkish, and able to read and write, with at least three weeks of chemotherapy treatment remaining.
Patients who met the following criteria were excluded from the study: having a known psychiatric disorder that could interfere with the intervention and data collection process, receiving chemoradiotherapy, or having cognitive, perceptual, or communication problems that could affect their ability to understand the training provided.
To determine the sample size, a pre-power analysis was performed using the G-Power 3.1.9.7 programme. For this analysis, the initial measurement total mean EORTC QLQ-C30 quality of life scale scores of the intervention and control groups in the study by Yüce and Yurtsever \[24\] were used. According to the analysis results, with an effect size of 0.65, a significance level of p\<0.05 in each group, a 95% confidence interval, and 80% test power, a minimum of 78 participants (39 participants each for the intervention and control groups) was determined. A total of 91 patients were reached during the specified dates, but 6 patients did not wish to continue the study and were therefore not included in the analysis. The study was completed with a total of 85 participants, including 43 in the intervention group and 42 in the control group.
After obtaining the necessary ethical committee and institutional approvals for this study, it was conducted through face-to-face interviews in a suitable room in the outpatient chemotherapy unit on the first day and the 21st day of chemotherapy for female patients diagnosed with breast cancer who met the inclusion criteria. On the first day of the interview, all participants were informed about the purpose and method of the study, and it was emphasised that participation in the study was entirely voluntary. Written informed consent was obtained through an informed consent form.
Taking into account the order of the randomisation table, one participant was included in the study each day, and on the first day of the interview, the researchers administered the Patient Information Form, the World Health Organisation (WHO) Oral Toxicity Criteria, the Oral Assessment Guide (OAG), European Organisation for Research and Treatment of Cancer (EORTC QLQ-C30) Version 3.0 Quality of Life Scale, Eastern Cooperative Oncology Group (ECOG) Performance Scale. In addition, the intervention group was trained on the use of the Oral Mucositis Prevention Patient Education Handbook, which was prepared by the researchers based on literature information and expert opinions. Participants in the intervention group received telephone consultations on days 7 and 14. The control group continued to receive routine nursing care. The second interview was completed on day 21, when both the intervention and control group patients returned for their next treatment cycle, using the WHO Oral Toxicity Criteria, ADR, and EORTC QLQ-C30 Version 3.0 Quality of Life Scale.
