An assessment of reliability and validity of the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire C30 among breast cancer patients in Qatar

Introduction: Breast cancer has been the most common cancer type that affects women worldwide and subsequent treatment is often associated with considerable psychological and quality of life (QoL). Aim: This study aimed to assess psychometric properties of the Arabic version of the European Organization for Research and Treatment of Cancer (EORTC) general QoL questionnaire (QLQ-C30) for breast cancer patients in Qatar. Materials and Methods: This is a cross-sectional hospital-based study conducted on 678 breast cancer patients using Arabic version of the EORTC QLQ-C30 tool. Results: The mean age of women was 47.7 ± 10.2 years and 33.4% of women had consanguineous parents. Six subscales out of the nine met the standards of reliability with coefficients ranging from 0.55 to 0.89. The mean score of all functioning scales was high >55. Advanced breast cancer stages of III–IV had higher symptomatic scores significantly than those in early stages for the physical function, cognitive, fatigue, insomnia, appetite loss, constipation, and financial difficulties. Correlation coefficients between each item ranged from –0.113 to 0.960, and item 21 (tense) and item 23 (irritable) had strongest negative correlations with their corresponding emotional functioning subscale, whereas items 29 (physical condition) and 30 (overall QoL) had the strongest positive correlation with Global Health/QoL subscale. Item 6 (limited work) showed a higher correlation with fatigue (r = 0.749). Likewise, item 19 (pain interfered with daily activities) of the pain subscale had higher correlations with physical functioning, role functioning, and fatigue subscales. Conclusion: Qatari Arabic version of the EORTC QLQ-C30 showed acceptable psychometric properties, which is a reliable and valid instrument, that can be used by oncologists