The Long-term Disease-specific Mortality of Low-risk Localized Prostate Cancer: A Prospective Population-based Register Study Over Two Decades

Rami Klaff, Johan Rosell, Eberhard Varenhorst, Gabriel Sandblom

Objectives To identify prognostic factors, and to estimate the long-term disease-specific and annual disease-specific mortality rates of low-risk prostate cancer patients from the early PSA era. Methods We studied data extracted from the Southeast Region Prostate Cancer Register in Sweden, on1300 patients with clinically localized low-risk tumors, T1-2, PSA level ≤10 µg/L and Gleason Score 2-6 or WHO Grade 1, diagnosed 1992-2003. The Cox multivariate regression model was used to evaluate factors predicting survival. Prostate cancer death rates per 1000 person-years were estimated for four consecutive follow-up time periods 0-5, 5-10, 10-15, and 15+ years after diagnosis. Results During the follow-up of overall survivors (mean 10.6 years; maximum 21.8 years) 93 patients (7%) died of prostate cancer. Cancer-specific survival was 0.98 (95% confidence interval (CI) 0.97-0.99), 0.95 (CI 0.93-0.96), 0.89 (CI 0.86-0.91) and 0.84 (CI 0.80-0.88) 5, 10, 15 and 20 years after diagnosis. The five-year increases in cancer-specific mortality were statistically significant (p<0.001). Patients with PSA ≥ 4 µg/L, managed initially with watchful waiting and age 70 years or older had a significantly higher risk of dying from their prostate cancer. Conclusion The long-term disease-specific mortality of low-risk localized prostate cancer is low, but the annual mortality rate from prostate cancer gradually increases. This indicates that some tumors slowly develop into lethal cancer, particularly in patients 70 years or older with a PSA level ≥ 4 µg/L.