Statistical Analyses
depression, anxiety
SECONDARY, RECURRENCE, BREAST CANCER
Deviations from the original analysis plan were made and finalized prior to data analyses and are described here. Descriptive analyses were applied to examine the differences between study groups at baseline. In intention-to-treat analyses, we applied linear mixed-regression models to examine the effect of the intervention on the primary outcome (distress) and secondary continuous outcomes (symptoms of anxiety and depression, breast cancer–specific HRQOL, fear of recurrence [no baseline data were included, and thus different effects of the intervention were allowed at all time points], sleep, cognitive function, and patient activation) in repeated-measures analyses, with a random effect for patients at 4 time points: baseline and 6-, 12-, and 18-month follow-up. The models assumed no difference between groups at baseline and were in the revised analysis plan, adjusted for randomization strata of age (<60 or ≥60 years) and treatment modality (none, adjuvant chemotherapy, or neoadjuvant chemotherapy).Statistical significance was interpreted at 2-sided In the revised analysis plan, we added exploratory analyses to examine whether the intervention effects were modified by age, years of education, social support, patient activation, and chemotherapy, using an interaction term between treatment group and the specific effect modifier. We conducted sensitivity analyses to examine the potential effect of missing data. The last-observation-carried-forward method in the revised analysis plan was replaced by multiple imputations using fully conditional specification methodsIntervention exposure and acceptability were assessed descriptively. Analyses were performed using R, version 4.0.4 (R Core Team)