Decision Analyses

While not specifically designed to determine the natural history of localized prostate cancer, several decision analyses have been published over the past 5 to 6 years that have addressed a similar question: the impact and utility of prostate cancer screening or treatment for localized disease. Many of the conclusions reached from these decision analyses are based on estimates of the natural history of the disease and therefore will be discussed in this chapter.

The first such analysis was performed by Fleming et al.30 The authors developed a series of outcomes for men 60 to 75 years of age, using estimates of the disutility of complications of treatment and of the disease and concluded that only with the most optimistic assumptions regarding treatment efficacy would treatment for prostate cancer affect patient outcomes. Unfortunately, for reasons that are inexplicable, of the five natural history studies of prostate cancer that the authors used to estimate what would happen to patients if tumors were left untreated, four studies reported on results of T1a disease. (As stated above, T1a disease unquestionably behaves in an indolent fashion and is undeniably different from T1b-T2 disease in all respects.) Additionally, the disutility of a variety of complications is very much at odds with the experience of any clinician who manages prostate cancer. For example, treatment-related impotence and incontinence were given disutility factors of 95% and 70%, respectively. While these indeed may seem reasonable, how it can be appropriate to give hormonally responsive metastatic prostate cancer a disutility rate of 90% is hard to understand. With these issues in mind, it is not surprising that the authors came to the conclusion that treatment had little effect on the natural history of the disease.

A similar analysis of prostate cancer screening was conducted by Krahn et al.31 The authors in this study used only one estimate for the natural history of the disease, that of Johansson. In addition to the problems inherent in using data from 70-year-old men to develop a decision analysis applied to men 50 to 70 years of age is the issue concerning the initial exclusion of men with poorly differentiated disease from Johansson's study. As can be seen from Table 13-1, while Johansson's study provides one estimate, there is considerable variation in the estimates of these outcomes. Of note, the authors did find that screening with PSA alone was relatively cost effective with an incremental cost-utility ratio of $42,000 per quality-adjusted life-year gained in 50-year old men. While this may seem to be a relatively high cost, it is very much in line with other therapeutic and preventive interventions.

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