Study design and procedure
breast cancer
SHIGA, BREAST CANCER
This was a worksite‐based, parallel‐group, open‐label cluster randomized trial. The 25 large supermarket stores were randomly assigned in a 1:2 ratio to two groups, the intervention group (mammography and leaflet) and the control group (leaflet).Prior to the randomization, consent was obtained from the health insurance society, the managers of the 25 stores, and individual employees. Eligible participants were female employees who were at least 40 years old and worked in one of the 25 stores. Participants were informed about the study in January–March 2018 and received a pre‐survey about their history of breast cancer and breast cancer screening. Written informed consent for data collection related to breast cancer, breast cancer screening, and health checkup data was obtained from all participants. Participants were blinded to the purpose of the study (i.e., to investigate the effect of offering mammography on breast cancer screening rate), to reduce confounding between grouping and screening behaviors.An independent statistician generated the randomized assignment sequence for the stores, which were stratified using the rate of employees who had attended breast cancer screening in the last 2 years. Ethical approval was obtained from the Ethics Committee of Shiga University of Medical Science (C2017‐201). The study protocol was registered in the University Hospital Medical Information Network Clinical Trials Registry (UMIN000030465).