Prostatic specific antigen and bone scan in the diagnosis and follow-up of prostate cancer. Can diagnostic significance of PSA be increased?

Prostate cancer (PC) is currently the most frequently diagnosed cancer in males and constitutes a major health issue in developed countries. On the other hand, the majority of PC cases are considered clinically not significant and certainly not lethal. These discrepancies highlight the need for the early detection of especially those cases that have aggressive features and call for early and radical intervention. The clinical use of prostatic specific antigen (PSA) towards this end is recognized as inadequate since PSA is prostate specific, but not a PC specific marker, as it is known to increase in other prostate diseases such as benign hyperplasia, inflammations, transrectal ultrasound examination, biopsy and after transurethral prostatectomy. However due to lack of other more specific markers, digital rectal examination combined with serum PSA are suggested for PC screening and diagnosis. With regard to advanced disease where bone involvement is the rule, nuclear medicine bone scan using radioactive bisphosphonates such as technetium-99m methylene-diphosphonate is quite common and reliable technique for detecting and monitoring bone metastases. The major advantage of nuclear scintigraphy is its ability to reveal bone metastases significantly earlier than the conventional X-ray imaging techniques. PSA density, velocity, doubling time and free to total PSA ratio increase the significance of serum PSA in diagnosing PC. The combination of an increased PSA (>20ng/mL) and a high biopsy Gleason score (>8) enhances the possibility of bone metastases (P<0001) and mandates a bone scan. In conclusion, serum PSA testing is currently recommended in symptomatic PC patients for disease staging and treatment monitoring and in asymptomatic selected population groups aged more than 50 years. It is reasonable to suggest that PSA density, velocity, doubling time and free to total PSA ratio or combining PSA with Gleason score shall greatly increase PSA specificity in detecting PC cases. Radioisotopic bone scan by SPET or PET can demonstrate osseous metastases at later stages of PC, but should also be applied in cases falsely considered as an early stage of PC, for better staging and for periodic follow-up of the disease.