Measurement of bone turnover in prostate cancer patients receiving intermittent androgen suppression therapy

PURPOSE Reports on clinical measurements of bone mineral density (BMD) in prostate cancer patients undergoing intermittent androgen suppression therapy (IAS) that allows for hormonal recovery between treatment cycles indicate decreased osteoporosis compared to continuous androgen suppression therapy (CAS). In the present study the effect of IAS on bone metabolism by determinations of CrossLaps, a biochemical marker of collagen degradation, were examined. METHOD In total 100 IAS treatment cycles of 75 patients with prostate cancer stages ≥ pT2 were studied. Clinical data and monthly laboratory tests (testosterone, prostate-specific antigen; PSA) of these patients were monitored together with measurements of C-terminal telopeptide collagen fragments using CrossLaps® ELISA assays. RESULTS During phases of androgen suppression (AS) lasting for 9 months serum testosterone (<1 ng/mL) and PSA (<2 ng/mL) levels were reversibly reduced, indicating partial growth arrest and apoptotic regression of the prostatic tumors. Serum CrossLaps concentrations peaked at the last 2 months of the AS phases (0.91 ± 0.25 μg/L; mean ± SEM) and were reduced below initial values (0.21 ± 0.43 versus baseline of 0.43 ± 0.06 μg/L) during therapy cessation periods until tumor progression-related increases. CONCLUSION Measurements of the serum concentration of CrossLaps in prostate cancer patients receiving IAS indicated that treatment cessation phases rapidly reversed increased bone degradation associated with AS phases, in strong agreement with the clinical observations reporting reduced loss of BMD in IAS when compared to CAS. In terms of clinical outcomes, IAS seems to be as effective as CAS while showing reduced side effects, as demonstrated here by the reduction of androgen-induced bone matrix degradation.