Biochemical markers for monitoring response to therapy: Evidence for higher bone specificity by a novel marker compared with routine markers

The aim of the present study was to compare a novel marker for high bone turnover with two routine markers for screening in prostate cancer patients. The markers were evaluated in two studies: (a) a cross-sectional study of 170 prostate cancer patients with local disease stratified by +/- lymph node metastases (N-0, N-1) compared with controls and (b) a longitudinal study of 40 hormone refractory prostate cancer patients stratified by skeletal involvement and followed during docetaxel (+/-BM) and zoledronate (+BM) treatment. Presence or absence of bone metastases (BM) was assessed by imaging techniques (magnetic resonance imaging or X-ray) and technetium-99m scintigraphy. The serum or urinary levels of alpha C-telopeptide of collagen type I (alpha alpha CTX), prostate-specific antigen (PSA), and total alkaline phosphatase (tALP) were assessed. PSA was elevated in both N-0 and N-1 patients compared with controls, whereas alpha alpha CTX was elevated only in N-1 patients. tALP exhibited no difference in any of the groups. In the treatment study, PSA decreased with treatment in both the - BM and +BM groups compared with baseline values, showing similar effect of docetaxel or docetaxel/zoledronate treatment on this marker. On the contrary, alpha alpha CTX and tALP did not decrease with docetaxel treatment in the - BM group compared with baseline, whereas it decreased significantly with docetaxel/zoledronate treatment in the +BM group, already after 1 month of treatment for alpha alpha CTX. Results suggest that alpha alpha CTX is superior to PSA and tALP for identifying patients having a high risk of metastatic disease and for monitoring skeletal progression in +BM prostate cancer patients during treatment.