Rejoinder

We appreciate very much Dr Kind’s insightful comments on our study [1]. Dr Kind points di-rectly to the heart of debate over quality of life (QOL) research: Is there a well-established, stan-dardized instrument that can measure all the rele-vant facets and dimensions of health-related QOL without bias? If such an instrument exists, can it really quantify, by an interval scale, the quality of life for our patients? QOL measurement has been increasingly em-phasized in evaluating the efficacy of cancer treatment [2]. Most studies compared the impact of different cancer treatments on QOL by report-ing the summary scores of QOL questionnaires [3]. The impact on survival is either considered sepa-rately from the observed QOL scores or ignored. This may result in a biased estimation of QOL because only living patients provide the follow-up QOL data for comparison [4]. The main feature of our model is to provide a composite measure, al-lowing for the impact of health service on both the quantity and quality of life, by direct integration of the QOL function and the survival function of a specific cohort [5]. The integration of the QOL and survival functions has a unit of score-time such as score-month or score-year, when QOL question-naires are used as the instrument for measurement. The results are best interpreted as the cumulative survival-weighted psychometric scores, which is the area under the curve of Q(t) vs. time, for the specific QOL dimension or facet [6]. The best way to test the validity of our statistical model is to put it in the context of controled clinical trials and correlate the results of the survival-weighted psy-chometric scores with other objective measure-ment of the patients ’ health status. The questionnaires we used in QOL research indeed reflect the values of the instrument devel-opers. Interpretation and decision on the relative importance of various dimensions of such profile measures can hardly be truly disinterested [7]. Therefore, the choice of questionnaires depends for a large part on the questions the researchers wish to address. The European Organization fo