Hydroxyproline excretion in the detection of occult bone metastases from breast cancer

When surgery fails to cure breast cancer it is due to disseminated micrometastases present at the time of operation. The measurement of urinary hydroxyproline (OHP) is a possible screening test for such metastases in bone. This study compared both a single and serial urinary OHP estimation with the axillary node status, the bone scan status and the subsequent clinical course. A single measurement did not correlate with the axillary node or bone scan status, neither was there a relationship with the subsequent clinical course. Serial OHP estimations, every 3 months for a year, increased the accuracy of the test such that node-positive patients had higher excretions than node-negative patients (p less than 0.05). Patients who subsequently died with bone metastases tended to have a higher excretion than those who remained disease free, although this did not reach statistical significance. No relationship existed between serial OHP estimations and bone scan status. We consider the measurement of urinary OHP to be insufficiently sensitive to detect bone micrometastases and it is only raised when a substantial amount of bone is involved.