Objectives. To study the long-term survival of patients with prostate cancer, determine the risk factors for prostate cancer death, and investigate the outcome of initially untreated localized prostate cancer and incidentally detected tumors.

Methods. The survival of 813 patients in a population-based cohort of patients with prostate cancer in Linköping, Sweden, diagnosed from 1974 to 1986, was analyzed.

Results. At 10, 15, and 20 years after diagnosis, the prostate cancer-specific survival rate of men with localized, initially untreated, prostate cancer was 85.0% (95% confidence interval [CI], 79.0% to 91.0%), 80.0% (95% CI, 72.5% to 87.5%), and 62.6% (95% CI, 43.0% to 82.2%). Age 70 years or older, advanced stage, and poor differentiation were risk factors associated with an increased risk of prostate cancer death. At 10 years, the prostate cancer-specific survival rate among men with localized tumors treated by expectancy was 90% (95% CI, 84% to 97%) for grade 1 tumors, 74% (95% CI, 60% to 89%) for grade 2 tumors, and 59% (95% CI, 29% to 90%) for grade 3 tumors. For patients with incidentally detected tumors, the grade of malignancy was a more important risk factor than tumor volume.

Conclusions. Patients with localized tumors have a favorable prognosis, even without initial treatment. However, when deciding on therapy, the grade of malignancy should be taken into account, as it has a great influence on survival. We did not see a tendency toward increased mortality when the patients were followed up for longer than 10 years after diagnosis.