The minimal clinically important difference in the treadmill six-minute walk test in active women with breast cancer during and after oncological treatments

Purpose To examine the minimal clinically important difference (MCID) in the treadmill 6-minute walk test (6MWT) in women with breast cancer. Materials and methods A secondary analysis of cross-sectional data from 112 women who were undergoing chemotherapy or had undergone anticancer treatment was conducted. Participants completed the 6MWT on a treadmill and the European Organization for Research and Treatment of Cancer Questionnaire (EORTC-QLQ-C30) twice, eight weeks apart. Change in the physical function domain of the EORTC-QLQ-C30 was used to classify the "positive change" subgroup (>= 5 points difference) and the "unchanged" subgroup (<5 points difference). This was combined with the distance difference from the 6MWTs, determining the MCID as the cut-off from the area under the receiver operating characteristic (AUROC) curve (anchor-based determination). The MCID was also determined from (1) the effect size and (2) the difference in standard error (SEM) of the results of the first and second 6MWT (distribution-based determination). Results The MCIDs in the during-chemotherapy group was 66.5 and 41.5 m and those in the after-treatment group to be 41.4 and 40.5 m (SEM and effect size based respectively). Conclusions The MCID in the treadmill 6MWT distance could be used to interpret changes in the physical health status of women with breast cancer.