UROLOGY

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Quality-of-Life Effects of Prostate-Specific Antigen Screening

 

The quality-adjusted life year (QALY) is a measure of disease burden, including both the quality and the quantity of life lived. It is used in assessing the value for money of a medical intervention. The QALY model requires utility independent, risk neutral, and constant proportional tradeoff behavior. The QALY is based on the number of years of life that would be added by the intervention. Each year in perfect health is assigned the value of 1.0 down to a value of 0.0 for death. If the extra years would not be lived in full health, for example if the patient would lose a limb, or be blind or have to use a wheelchair, then the extra life-years are given a value between 0 and 1 to account for this. Under certain methods, such as the EQ-5D, QALY can be negative number.

 

After 11 years of follow-up, the European Randomized Study of Screening for Prostate Cancer (ERSPC) reported a 29% reduction in prostate-cancer mortality among men who underwent screening for prostate-specific antigen (PSA) levels. However, it is not known whether the side effects resulting from unnecessary procedures based on the overdiagnosis of prostate cancer counterbalance the benefit of the reduced mortality. As a result, a study published in the New England Journal of Medicine (2012;367:595-605), used Microsimulation Screening Analysis (MISCAN) to predict the number of prostate cancers, treatments, deaths, and quality-adjusted life-years (QALYs) gained after the introduction of PSA screening. Based on the data, various screening strategies, efficacies, and quality-of-life assumptions were modeled.

 

Results showed that per 1,000 men of all ages who were followed for their entire life span, annual screening of men between the ages of 55 and 69 years would result in nine fewer deaths from prostate cancer (28% reduction), 14 fewer men receiving palliative therapy (35% reduction), and a total of 73 life-years gained (average, 8.4 years per prostate-cancer death avoided). The number of QALYs that were gained was 56 (range, – 21 to 97), a reduction of 23% from unadjusted life-years gained. To prevent one prostate-cancer death, 98 men would need to be screened and 5 cancers would need to be detected. Screening of all men between the ages of 55 and 74 would result in more life-years gained (82) but the same number of QALYs (56).

 

According to the authors, the benefit of PSA screening was diminished by loss of QALYs owing to post-diagnosis long-term effects and that longer follow-up data from both the ERSPC and quality-of-life analyses are essential before universal recommendations regarding screening can be made.

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