Localized prostate cancer. Relationship of tumor volume to clinical significance for treatment of prostate cancer

TLDR

Prostate cancer occurs in about 8 % of men, yet many cases are microscopic and clinically insignificant, prompting examination of cystoprostatectomy specimens to assess true prevalence. The authors used SEER data to estimate lifetime prostate cancer risk, then examined 139 cystoprostatectomy specimens and measured the largest tumor volume in each using histologic morphometry. Among the 139 specimens, 55 (40 %) harbored prostate cancer, and the largest 11 tumors—each >0.5 ml—accounted for 7.9 % of cases, suggesting that only tumors larger than 0.5 ml represent the clinically significant 8 % of men who will develop overt disease, while the majority of smaller cancers are unlikely to progress.

Abstract

Using the Surveillance, Epidemiology, and End Results Program of the National Cancer Institute and American total mortality rates, the authors calculated the probability at birth of having a diagnosis of prostate cancer within a man's life to be 8.8% and then subtracted the incidence of microscopic Stage A cancers too small to ever be clinically significant. This gave a final probability of 8%.Prostates were examined after 139 consecutive unselected cystoprostatectomies from patients with bladder cancers in whom it was unknown whether they had prostate cancer. Prostate cancer was found in 55 patients (40%); the volume of the largest cancer in each specimen was determined using histologic morphometry. The authors identified the 8% of these 139 cytoprostatectomy specimens with the largest volume of prostate cancer.The largest 11 of the 55 cancers represented 7.9% of the total 139 samples. These cancers ranged in volume from 0.5-6.1 ml, representing only 20% of all patients with prostate cancer.If the strong evidence is accepted that cancer progression is proportional to cancer volume, it was concluded that prostate cancers larger than 0.5 ml appear to correspond to the 8% of men who will be diagnosed with a clinically significant carcinoma, as derived previously. Conversely, those 80% of prostate cancers smaller than 0.5 ml probably are not likely to reach a clinically significant size in view of the long doubling time of this cancer.