Statistical analysis plan for the China Workplace Cancer Prevention Comprehensive Intervention Study: a stepped-wedge cluster-randomized controlled trial

Abstract Background This paper describes the protocol amendments and statistical analysis plan (SAP) for the China WorkplacE CANcer Prevention Comprehensive Intervention Study (WECAN), which aims to develop and evaluate a workplace-based model for cancer prevention in China. Methods WECAN is a stepped-wedge, cluster-randomized controlled trial implemented in 15 workplaces across three cities in China since April 2023. A total of 840 employees (originally planned as 750) were randomly selected for assessment through six surveys (originally five) conducted at 6-month intervals. After the second survey, workplaces were randomly assigned to initiate the intervention in three sequential steps, with five workplaces assigned to each step. A mobile application named “Healthy Workplace” will be developed to support the intervention, including both online and offline health-related activities for employees. In addition, employers will implement supportive policies, environments, and benefits to encourage the adoption of healthy behaviors. The primary outcome will be the change of the Chinese-adapted Healthy Lifestyle Index Score, comprising five components: smoking, alcohol consumption, physical activity, diet, and body mass index. All analyses will be performed based on the intention-to-treatment (ITT) principle. The effect of the intervention on primary outcomes will be tested using linear mixed models after adjusting for time, time and intervention interaction, the clustering effects of workplaces and city, and other confounders. This publication is based on a formal statistical analysis plan document that was finished and signed on 22 July 2025. Discussion Publishing a statistical analysis plan mitigates trial reporting bias and offers a concise outline of predetermined analyses. Crafting a fitting statistical analysis plan necessitates thoughtful deliberation on the optimal analysis population, methodologies, and models. This plan aimed to strike a balance between minimizing bias, optimizing test efficacy and precision, and generating results that meaningfully reflect the population-level impact of the intervention. Trial registration WECAN project was registered in Chinese Clinical Trial Register on April 14, 2022 (ChiCTR2200058680).