The researchers used information that had been collected in a large study of men with prostate cancer.
Within 6 months of diagnosis, the men completed a survey on which they indicated whether they had other
medical problems (such as lung or heart disease). Their medical records were also reviewed to find details
about the prostate cancer and its treatment. The researchers followed the men in the study and evaluated
relationships among other diseases that were present; what kind of treatment was given; and whether the men
died and, if so, whether they died of prostate cancer or something else.