Relationship Between ALP, PSA, PSA-Based Parameters And Bone Metastasis In Prostate Cancer

Objective : To investigate the relationship between ALP, PSA, PSAD(PSA density)and free-to-total PSA (fPSA/tPSA)ratio with bone metastasis in prostate cancer, and the role of these parameters in the prediction of bone metastasis of prostate cancer.Method:A total of 167 patients with histologically diagnosed prostate cancer were treated in our hospital from Sep. 2005 to Feb. 2009. Serum PSA levels were measured using the microparticle enzyme immunoassay method by Abbott AXSYM autoanalyzer. Prostate volume was estimated by abdominal ultrasound measurements using the prostate ellipse formula(0.52×length×width×height). PSAD(PSA/volume) was calculated by dividing serum PSA level by prostate volume. Serum ALP levels were measured using automatic biochemistry analytic method by OLYMPUS autoanalyzer AU5400 and AU640. ECT, CT/MRI and bone biopsy were used for identifying bone metastasis in patients with prostate cancer.Results :Of 167 consecutive patients, 104 had bone metastasis (62.3%). ALP, PSA and PSAD in bone metastasis group were higher than none bone metastasis gorup, respectively (P<0.001), no significant difference existed for fPSA/tPSA between bone metastasis group and none bone metastasis group (P>0.05). Bone metastasis positive rate: PSA levels of > 50ng/mL was higher than levels of 20-50ng/mL, 10-20ng/mL and≤10ng/mL(P<0.05); ALP levels of > 90U/L was higher than levels of≤90 U/L(P<0.05); PSAD > 0.4ng/mL·cm3 was higher than PSAD≤0.4ng/mL·cm3 (P<0.05). Sensitivity, specificity, positive predictive value and negative predictive value of ALP cut-off of 90U/L were 55.77%, 74.60%, 78.38% and 50.54%, respectively. Sensitivity, specificity, positive predictive value and negative predictive value of PSA cut-off of 50ng/mL were 85.58%, 77.78%, 86.41% and 76.56%, respectively. Sensitivity, specificity, positive predictive value and negative predictive value of PSAD cut-off of 0.4ng/mL·cm~3 were 97.12%, 38.10%, 72.14% and 88.89%, respectively. PSAD cut-off of 0.4ng/mL·cm~3 combined with PSA cut-off of 50ng/mL and ALP cut-off of 90U/L were showed the best sum of sensitivity, specificity, positive predictive value and negative predictive value, which were 100%, 79.17%, 91.38% and 100%, respectively.Conclusion:ALP, PSA and PSAD are good parameters used in the prediction of bone metastasis in prostate cancer. Although further studies are needed to determine optimal cut-off value to be used in clinical practice, PSAD cut-off of 0.4ng/mL·cm~3 combined with PSA cut-off of 50ng/mL and ALP cut-off of 90U/L seems to be useful for the prediction of bone metastasis in prostate cancer patients. This would be justified its utility in clinical practice reducing unnecessary ECT and CT/MRI examinations, which are relatively expensive for Chinese patients.