Aminoterminal propeptide of type I collagen and bone alkaline phosphatase in the study of bone metastases associated with prostatic carcinoma

The aim of this work was to evaluate the usefulness of serum aminoterminal propeptide of type I collagen (PINP) in the early detection of bone metasta ses associated with prostatic carcinoma. The results were compared with tho se of bone isoenzyme of alkaline phosphatase (bAP). Levels of total alkalin e phosphatase (TAP) and prostatic specific antigen (PSA), related to the ex istence of bone metastases, are also evaluated. Fifty-five male patients aged 70-80 years were studied. Nine presented a be nign prostatic hyperplasia (BPH) and the rest clinically confirmed prostati c cancer. Cancer patients were classified in accordance with the staging gr ouping of the International Union Against Cancer/American Joint Committee o n Cancer TNM 1992 Revision: stage 0 or BPH (n=9), I (n=6), II (n=12), III ( n = 18) and IV (n = 10). According to this classification, patients of grou ps BPH, I, II and III have no evidence of metastases. Those of stage IV pre sent any type of metastases. In the case of this work, all patients of grou p TV presented bone metastases. Some patients of group BPH, I and II were u ntreated. The rest of the patients were under treatment (radical prostatect omy, telecobaltotherapy or hormonal therapy) for a period of between 6 mont hs and 15 years. Serum PSA (Quimioluminiscence, IMMULITE), PINP (RIA, Orion Diagnostica), bAP (IRMA, Tamdem R-Ostase, Hybritech), and TAP (autoanalyze r) were determined. We found the following sensitivities and specificities (relating the presen ce of bone metastases to values higher than the upper limit of normality an d, in the case of PSA, to values higher than 100 mu g/L): (1) PINP: 100% (1 0/10) and 87% (39/45), (2) bAP: 90% (9/10) and 82% (37/45), (3) TAP: 60% (6 /10) and 93% (42/45), (4) PSA: 40% (4/10) and 100% (45/45). These results suggest that PINP and bAP are adequate biochemical markers of bone formation to be used in the detection of bone metastases in prostatic carcinoma, improving the sensitivity and specificity of TAP and PSA. With respect to PINP, bAP presents the disadvantage of its cross-reactivity with liver isoenzyme.