IMPACT OF LIFE EXPECTANCY AND TUMOR DOUBLING TIME ON THE CLINICAL-SIGNIFICANCE OF PROSTATE-CANCER IN JAPAN

Theoretical projected prostate cancer volume at the time of expected d eath was determined based on patient age and index cancer volume at di agnosis, assumed cancer volume doubling time and life expectancy of th e Japanese male population. Based on the data obtained, evaluation was made of the results for 104 consecutive radical prostatectomy cases w ith no prior treatment. Clinically insignificant cancer in 104 prostat ectomy specimens was found to occur at 4.8, 10.6, 15.4 and 26.9% for t umor doubling times of 2, 3, 4 and 6 years, respectively. Assuming a 2 -year doubling time with clinically insignificant cancer excluded, onl y 36.4% of significant cancers could be considered potentially curable and with a 3-year doubling time, 32.3%. For 4- and 6-year doubling ti mes, only 30.7 and 25.0% of the clinically significant cancers were po tentially curable, respectively. Approximately half of these insignifi cant cancers were clinically stage T1c disease. In all stage T1c cases , 8.8-47.1% was considered insignificant, depending on tumor doubling time. Patient life expectancy and tumor doubling time significantly de termine the outcome of treatment for prostate cancer, especially in el derly males with higher risk of mortality. The outcome of radical pros tatectomy is less satisfactory with these factors taken into considera tion. Many patients with stage T1c disease may eventually prove to req uire no treatment.