Objectives:  To develop and validate the Thai version of the functional assessment of cancer therapy with nasopharyngeal cancer subscale (FACT-NP) with the abbreviated version of the World Health Organization Quality of Life-BREF instrument (WHOQOL-BREF).

Material and Methods: A cross-sectional study was performed in the Radiology Department between January 2014 and October 2016. Inclusion criteria: nasopharyngeal carcinoma patients aged greater than 18 years. Exclusion criteria:  no comprehension of the Thai language, had other cancers (except for skin cancer and diagnosed with impaired cognition and/or overt psychosis), major depression or delirium. After signing the consent form, participants were interviewed and self-completed FACT-NP and WHOQOL-BREF. The structure of the FACT-NP was determined with exploratory factors analysis. The internal reliability of identified domains was evaluated using Cronbach’s alpha. The correlation between domains of the modified FACT-NP and the domains of WHOQOL-BREF were examined with Spearman’s correlation. Known-group validity was determined by comparing patients with different sociodemographic and clinical characteristics using the T-test, Ranksum test and analysis of variance. A p-value of less than 0.05 was considered significant.

Results: This study was terminated early due to a long accrual period. Of the 230 patients included in the study, only 220 completed both FACT-NP and WHOQOL-BREF. Exploratory factor analysis showed an accumulative variance of 0.56 with 4 factors. The internal reliability of modified FACT-NP was 0.92. There was moderate correlation between modified FACT-NP and WHOQOL-BREF. Both the modified FACT-NP and WHOQOL-BREF could identify differences between the groups.

Conclusion: The Thai modified FACT-NP was found to be both valid and reliable for measuring the quality of life in Thai nasopharyngeal cancer patients.