Quality of life assessment in a cross-cultural context: Use of the Rotterdam Symptom Checklist in a multinational randomised trial comparing CMF and Zoladex (Goserlin) treatment in early breast cancer

Aim: The aim of the study is to investigate quality of life (QoL) in the context of a multinational trial. The questions addressed are: is the Rotterdam Symptom Checklist (RSCL) 1) feasible and 2) reliable in cross cultural research, 3) is earlier Validation confirmed in a multinational trial and 4) are there systematic differences in QoL accross cultures? Patients and methods: Patients with histologically confirmed stage II, node positive breast cancer, were randomised in a multinational trial (the 'ZEBRA-study') comparing standard chemotherapy (CMF) or temporary ovarian ablation by treatment with a LHRH analogue (Zoladex, Goserlin). Patients originating from 13 countries completed a QoL questionnaire at baseline and three months after the start of treatment. Results: 1) The questionnaire was completed by 689 patients at the first and 544 at the second measurement (response 78% and 68% respectively). The proportion of missing data was <2.5% for 87.8% and 92.7% of the items at the respective time points. 2) Reliabilities of the physical and psychological distress scale were ranging from 0.68 to 0.90 across cultures. Reliability of the activity scale ranged from 0.42 to 0.89. 3) The structure at baseline was in agreement with the two factor structure proposed earlier. 4) Cross-cultural comparison indicated a systematic difference in QoL across cultures (P = 0.0028-<0.0001) as well as a difference in change across cultures. Conclusions: QoL assessment using the RSCL proved feasible in the context of multinational clinical trials. Psychometric qualities were satisfactory. Systematic differences in QoL were found between cultures. This finding implies that in multinational clinical trials, treatment comparisons with respect to QoL should carefully account for a differential impact of cultures on the results.