Assessing the reliability and validity of comprehensive score for financial toxicity (COST) among radiation oncology patients in India: a cross-sectional pilot study

BACKGROUND: Besides physical toxicity, cancer care imposes significant financial distress referred to as financial toxicity (FT). FT has become a growing concern among cancer patients. Researchers have associated FT among cancer patients with clinical outcomes like mortality, poor quality of life and non-adherence. Currently, no reliable tools are available for assessing FT among cancer patients in India. The aim of this pilot study was to test the reliability and validity of the Comprehensive Score for Financial Toxicity (COST) questionnaire among patients undergoing radiotherapy in India. MATERIAL AND METHODS: This cross-sectional pilot study was conducted among head and neck cancer patients on follow-up in radiation oncology department. The reliability of COST measure was assessed using Cronbach’s α. The underlying construct of COST was verified by Exploratory Factor Analysis (EFA). EFA was performed using parallel analysis technique. RESULTS: Based on inclusion and exclusion criteria, the COST questionnaire was administered to 29 patients using the interview method after written informed consent. The COST measure demonstrated excellent reliability with Cronbach’s α of 0.92. A Kaiser–Meyer–Olkin of 0.87 verified the sample adequacy and a p-value of ˂0.001on Bartlett’s sphericity test indicated that the strength of the correlation between 11 COST items was good to perform the EFA. Parallel analysis technique identified one factor on scree plot with eigenvalue of 6.21 explaining 56.5% of the variance by non-rotated solution. All the factor loadings in one factor model were ˃0.3 (range 0.35–0.97). The factor loadings indicated that the underlying construct can be considered as one factor domain as intended by the original COST development study. However, Chi-square goodness of fit test revealed the one factor model did not adequately depict the data. However, the results were consistent with the construct obtained in the original scale development study. CONCLUSION: This pilot study demonstrated excellent reliability of COST for measuring FT among radiation oncology patients. Further studies are warranted to study the clinical implications of FT in the Indian population for making better strategies and policies to ease the financial burden on cancer patients.