1486 QUALITY OF LIFE WITH PROSTATIC CANCER

EDITORIAL COMMENT

In a very ambitious report on quality of life (QOL), Borghede e t al go beyond instrument development and description. In touching on dimensionality and psychometric and empirical validity-method- ological issues that have been minimally addressed in contemporary prostate cancer QOL research-the authors challenge the urological community to consider QOL in a manner that is organized, efficient, interpretable, and useful. A thorough examination of methodological issues will bring a day when we can move beyond describing QOL to our patients to effecting interventions that improve QOL.

As implied in this paper, our first task is to simplify communica- tion. Many measures of QOL float unencumbered through our liter- ature, but many is not necessarily better. By simplifylng dimension- ality, exploratory factor analysis opens the door to a rational elimination of items that reduces redundancy while retaining rich- ness. In the present dataset, exploratory factor analysis can answer important questions. First of all, are “disease-specific” dimensions really distinct from “generic” dimensions as implied by the restricted analysis? The authors’ observation that bowel and gastrointestinal items loaded together when the latter were included suggests tha t a distinction would be rejected. Secondly, how much of the variance is explained by each dimension? Do we need to develop new scales, or have we explained most of the variance? As observations are made with exploratory factor and other analyses, we will confront new questions that may be hard to answer. How does one explain a QOL dimension that relies on flatulence and leg/penile swelling? Is it disease-specific? Why is it stage specific? What are its causal origins? Why were all functional scores reduced in the presence of psychiatric disease, when a commonly accepted 2-dimensional model of health- related QOL. proposed in the Medical Outcomes Study,’ states that physical and emotional functions are a function of medical and psychiatric health, respectively?

Reducing dimensionality is a useful but solitary step on the road to interventions that improve QOL. Importantly, reduction of items will facilitate concurrent and/or sequential measurement of determi- nants and/or sequelae of poor QOL. Adding such context to QOL analyses is the only way in which we will develop theoretical models and then rational interventions that target QOL As QOL meas- urement is simplified and other measures are added, we will also shift our analyses from comparison, for example surgery vs. radia- tion, to “regression,” given QOL distribution, which input variable best explains it? As our recent experience shows, “regression” ap- proaches can yield rather nonintuitive results, for example that emotional QOL in prostate disease depends more on ability to make meals than satisfaction with sex life.2

In survival research, end points are measured the same way ev- erywhere, but in QOL research, end points are measured differently because measurement relies on language. TO develop maximall,, generalizable models of QOL will require reliable translations of QOL instruments. However, developing reliable translations of seemingly simple questions for example “how often have YOU leaked urine,” can be comp1icated.Y Even more complicating is the observation that language can affect perception. Thus, in our study of Spanish and English speaking men, we discovered that the same man answered questions about how his health affected his social life differently when the question was asked in Spanish than when it was asked i n English.

In the ideal world, all investigators would embrace a single multi- lingual measurement ofQOL in prostate cancer. but in the real world investigators will embrace many instruments. Fortunately, tech. niques are available to establish the equivalence of scaled measures of QOL.4 which will enable comparisons of studies that use different instruments.

The prostate cancer QOL field is young and largely dedicated to instrument development and cross-sectional description, which is minimally useful a t the bedside. At this early juncture, the Journal of Urology-a journal for practicing urologists-is providing a stable and inclusive forum for expression of formative issues. This forum will bring a faster maturation of the field, which is very good news for our patients.

Arnon Krongrad Urology Veterans Affairs Medical Ceritrr Miami, Florida

1. McHorney, C. A,, Ware, J., John E. and Raczek, A. E.: The MOS 36-item short-form health survey (SF-36): 11. psychometric and clinical tests of validity in measuring physical and mental health constructs. Med. Care., 31: 247, 1993.

2. Krongrad, A., Granville, L. J . , Burke, M. A., Golden, R. M., Lai, S., Cho, L. and Neiderberger, C. S.: Predictors of general quality of life in patients with benign prostate hyperplasia or prostate cancer. J . Urol., 157: 534, 1997.

3. Krongrad, A., Perczek, R. E., Burke, M. A., Granville, L. J . , Lai, H. and Lai, S.: Reliability of Spanish translation of selected urological quality of life instruments. J . Urol., 158: 493, 1997.

4. Gonin, R., Lloyd, S. and Cella, D.: Establishing equivalence between scaled measures of quality of life. Qual. Life Res., 5 20, 1996.