Serum N-telopeptide (NTx) is material in type-1 collagen--the protein of connective and other tissue--that is released when cells called osteoclasts function in the breakdown and resorption of bone tissue. It is a marker of bone resorption. These investigators wanted to determine whether NTx might act as a marker for bone metastases in advanced prostate cancer.

They took sera from 39 men with prostate cancer and a positive bone scan, and from 45 men with prostate cancer and a negative bone scan. Serum NTx levels were compared to serum PSA levels between the two groups. They found that serum NTx levels were a very significant predictor of bone metastases in men with prostate cancer, exceeding the predictive potential of the PSA test.