Development and validation of the functional assessment of cancer therapy nasopharyngeal cancer subscale

Background. We aimed to develop a quality-of-life subscale for nasopharyngeal carcinoma (NPC) and validate the functional assessment of cancer therapy-nasopharyngeal (FACT-NP). Methods. The FACT-NP was tested cross-sectionally in survivors of postirradiated NPC (n = 357) and was administered to newly diagnosed patients (n = 160) before, at the end of, and 3 months after radiotherapy (RT). Results. Each FACT-NP domain was internally consistent (Cronbach's alpha = 0.87-0.90). The test-retest reliability for each subscale was satisfactory (intraclass correlation coefficient = .73-.88). Concurrent validity was suggested by the moderate to strong correlations between the FACT-NP and the Quality of Life-Radiation Therapy Instrument-Head and Neck (QOL-RTI-H&N) subscales (Pearson r = .39-.84). The FACT-NP was responsive to clinical changes from pretreatment to 3 months after RT (effect sizes > 0.6 for clinically relevant subscales). The pooled data for multitrait scaling analysis showed satisfactory item internal consistency and item discriminant validity (100% and 90% scaling success, respectively). Conclusion. The FACT-NP is a reliable and valid instrument for measuring QOL in patients with NPC.