Serum tartrate-resistant acid phosphatase 5b as a marker of bone metastases in prostate cancer

Calcif Tissue Int 72, Abstract P10

Maddison R¹, Kyd PA¹, Swinn M², Fairney A³

¹Dept of Chemical Pathology, St Mary's Hospital, London
²Dept of Urology, St Mary's Hospital, London
³Imperial College Faculty of Medicine, London

Abstract

Prostate cancer is the most common carcinoma in men, often complicated by metastases which are usually assessed by bone scintigraphy, an expensive technique with limited availability. Metastases are predominantly osteosclerotic, though with evidence of increased resorption, and various bone markers have been studied as indicators for bone metastasis. A recently-introduced method for serum tartrate - resistant acid phosphatase TRAP 5b (BoneTRAP, SBA, Oulu Finland), is osteoclast- specific, independent of liver and renal function and relatively convenient. This study evaluates its clinical utility in the detection of bone metastases in prostate cancer, and compares TRAP5b with conventional serum bone markers of formation (bone alkaline phosphatase, BALP) and resorption (serum C-telopeptide, CTx).

Serum TRAP 5b, BALP (Metra) and CTx (Nordic Bioscience) were measured in men assigned to the following groups based on bone scintigraphy, biopsy, Gleason score and serum PSA : benign prostatic hypertrophy (n=17), prostate cancer without metastases (n=28) and prostate cancer with metastases (n=27). A local reference range derived from 52 men aged 40-90 years with no known prostate disease gave TRAP5b values of 0.8-5.7U/L. TRAP 5b was significantly elevated in patients with bone metastases compared with those without (7.1 (1.27) mean (SEM) v 3.4(0.3) U/L, p < 0.001) and with benign prostatic hypertrophy (2.6(0.2)) U/L, p < 0.0001). There was a significant correlation of TRAP 5b with BALP (p < 0.0001), with serum CTx (p < 0.0001) and with PSA (p < 0.01), but not with Gleason Score. ROC analysis showed TRAP5b (AUC 0.75(0.07)) to have similar diagnostic utility in detecting bone metastases to BALP (AUC 0.79(0.06)) and serum CTx (AUC 0.74(0.07)).

We conclude that TRAP 5b appears to have a potential use for the detection of early metastases in prostate cancer.