Possible substantive improvements in the structure of the Quality of Life in Adult Cancer Survivors (QLACS) scale? A study based on its Spanish version.

ABSTRACT

PURPOSE: Quality of Life in Adult Cancer Survivors (QLACS) scale is one of the most commonly used and validated measures to assess the Health-Related Quality of Life (HRQoL) in this population. However, there are some aspects related to its structure that still deserve consideration. The aim of this study was to test the substantive improvement over the original QLACS structure resulting from several proposals reflected in the literature. METHOD: Using a cross-sectional design and Confirmatory Factorial Analysis, we explored those proposals. Reliability, convergent validity, and factor invariance across three cancer survivorships phases (re-entry, early, and long term) were also analyzed. 1.862 post-treatment survivors of diverse cancer types completed the Spanish versions of QLACS, Brief Symptom Inventory-18 (BSI-18), and Subjective Happiness Scale (SHS). RESULTS: The original model with twelve domains, grouped (with the exception of benefits) into a single total score, versus two subtotal (Generic and Cancer-specific) obtained a good fit. The values of Cronbach's alpha, Composite reliability, Average Variance Extracted indexes, and Pearson correlations supported the internal consistency and temporal stability (interval of 2-3 weeks) of the QLACS. Results also showed its adequate convergent validity and an invariant factor structure across survival periods (re-entry survivorship, early survivorship, long-term survivorship). CONCLUSION: In its original structure, albeit the replacement of the scores on the two subscales by a total score, our results support QLACS as a valid and useful tool for the assessment of HRQoL in post-treatment cancer survivors throughout the different survival phases.