Factor Structure and Longitudinal Invariance of the Cancer Behaviour Inventory: Assessing Cancer‐Coping Self‐Efficacy in Patients With Moderate‐to‐High Symptoms

ABSTRACT Background The Cancer Behaviour Inventory–Brief Version was designed to assess cancer‐coping self‐efficacy in clinical and research settings where minimising patient burden is essential. However, there is no evidence of its longitudinal validity. Although widely used in cancer research, the lack of evidence for longitudinal invariance significantly undermines its validity in studies spanning multiple time points. Establishing longitudinal invariance enables valid comparisons over time, enhancing our confidence in applying it in longitudinal research. Aim To examine the factor structure of the measurement and test its longitudinal invariance across four time points in cancer patients experiencing moderate‐to‐high symptoms during curative cancer treatment. Design A longitudinal psychometric evaluation. Methods This is a secondary data analysis of a randomised controlled trial in patients with moderate‐to‐high symptoms undergoing cancer treatment ( N = 534). We conducted longitudinal invariance tests for the measurement using four time points. Other psychometric tests included confirmatory factor analysis, reliability analyses and correlations. Results Our confirmatory factor analysis supported the four‐factor, 12‐item structure for the Cancer Behaviour Inventory–Brief Version. Items 1 and 6 were found to be moderately correlated. The resulting 12‐item measure demonstrated good internal consistency, with convergent and divergent validity supported by correlations with selected instruments. Finally, longitudinal invariance was tested, which revealed strict measurement invariance across four time points (CFI = 0.930, RMSEA = 0.045, SRMA = 0.056). Conclusion We found that the factor structure of the Cancer Behaviour Inventory–Brief Version remained stable over four time points in a sample of patients having moderate to high symptoms under cancer treatment. This supports its accountability for examining the changes in cancer‐coping self‐efficacy among cancer patients over time in longitudinal studies. Implications This study confirms that Cancer Behaviour Inventory–Brief Version has adequate internal consistency and demonstrated evidence of construct validity. Our conclusion of strict longitudinal invariance supports its credibility for continuous assessment of cancer‐coping self‐efficacy to evaluate patient outcomes and intervention processes over time in clinical and research settings. Patient or Public Contribution No patient or public contribution.