Introduction: Recently, it has been recognized that a more comprehensive assessment of the cancer patient isnecessary and that the evaluation of outcomes must move beyond traditional biomedical endpoints to includeassessments of the impact of disease and its treatment on patients’ quality of life. The European Organizationfor Research and Treatment of Cancer has developed a 30-item quality of life questionnaire to obtain informationabout the impact of disease and treatment on the daily living of cancer patients. This questionnaire has beentranslated into many languages and used in various countries. However, version 3.0 has not yet been validatedfor use with Iranian patients. The aims of the present study were therefore to evaluate the reliability and validityof the new QLQ-C30 questionnaire. Method: We conducted a cross-sectional study on 132 random samples ofbreast cancer patients. Reliability was evaluated through the internal consistency of multi-item subscales.Pearson’s correlations of an item with its own scale (corrected for overlap) and other scales were calculated toevaluated convergent and discriminant validity. Clinical validity was evaluated by known-group comparisons.All calculations were performed using SPSS.V.13 software. Results: In the reliability analysis, most scales fittedthe criteria except the fatigue (Alpha 0.65), pain (Alpha 0.69) and nausea and vomiting scales (Alpha 0.66).Convergent validity was evidenced by item own subscale correlation above 0.40 for all multi-item subscales.Item discriminant validity was successful in all analyses except for item 4 of the physical functioning scale.Results of the group based analysis show significant differences in QLQ-C30 functioning and symptom scores,where patients with higher grade have the worst outcome(P<0.05). Conclusion: The Iranian version of EORTCQLQC30 is a reliable and valid QOL measure for cancer patients which indicates that it can be used in clinicaland epidemiological cancer research.
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