Health-related quality of life in men with metastatic prostate cancer: the misleading effect of lead-time bias.
To ascertain whether the difference in health-related quality of life, which appears to be worse in men with metastatic prostate cancer when the metastases are noted at initial diagnosis than during follow-up after treatment for clinically localized disease, can be attributed to previous local control or to some form of measurement bias. We analysed by univariate and multivariate methods 375 men with metastatic prostate cancer who were enrolled in CaPSURE, a national observational cohort of patients with prostate cancer treated in community and academic settings throughout the USA. In particular, we assessed whether group differences in health-related quality of life were explained by the timing of metastatic diagnosis in the course of their disease. Health-related quality of life was measured with the RAND 36-Item Health Survey (SF-36). After controlling for relevant covariates (age, comorbidity and ethnicity), multivariate models suggested that men whose metastases were noted at the time of initial diagnosis scored 5-15 points worse in all eight domains of the SF-36. Men who are diagnosed with metastatic prostate cancer during the follow-up after treatment for clinically localized disease report a better quality of life than those who are metastatic at the time of diagnosis, not because the primary treatment confers any benefit but because they are followed more closely over time and diagnosed with metastases earlier in the course of their disease. This apparent difference in quality of life is an effect of lead-time bias in the diagnosis of metastasis.