The Study for Accuracy Assessment of Free PSA Density for Prostate Cancer Detection in Male Patients with High PSA

Background: Prostate cancer detection is currently based on serum PSA with a digital rectal examination which is neither specific nor sensitive, which caused many unnecessary prostate gland biopsies that are highly expensive and can result in unwanted complications. Serum free PSA increases with a larger prostate gland,yet declines with a gland that contains cancer cells, thus prompting the hypothesis that calculating the ratio of serum free PSA against prostate gland volume provides the so-called “free PSA density” which can be utilized to improve prostate cancer detection. Methods: Male participants were deemed eligible if they are at risk of prostate cancer with a PSA level of 4-10 ng/dL and aged between 50-75 years. Serum PSA and serum free PSA were obtained concurrently, followed by transrectal ultrasonography for prostate volume calculation and biopsy of the gland. Also reported are the sensitivity, specificity, positive predictive value, negative predictive value, accuracy, and receiver operating characteristic(ROC) with area under the ROC curve(AUC) of serum PSA, %free PSA ratio, free PSA density and PSA density. The AUC of the variables were compared with the free PSA density and reported. Results: The free PSA density cut point values which provided the highest accuracy was 0.025mg/mL/cc, which had 61.5% sensitivity and 67.25% specificity. The ROC results indicate that %free PSA ratio had the best AUC at 0.86. Free PSA density and PSA density have AUC at 0.65 and 0.61, respectively. Meanwhile, serum PSA had the worst AUC of 0.54. The researchers also calculated different AUCs of other variables to free PSA density. Finally, the AUC of free PSA density was significantly better than the reference standard tool serum PSA (p=0.022). Conclusions: Prostate cancer is an emerging cancer among elderly men. Frequent use of serum PSA as a screening tool allows earlier diagnosis of this cancer but with the expensive of unnecessary further investigations. Most novel and promising tools are too expensive to be used as a generalized screening tool. From this study, free PSA density may be a reasonable alternative tool for detection of prostate cancer.