Transient increase in total serum alkaline phosphatase predicts radiological response to systemic therapy in breast cancer patients with osteolytic and mixed bone metastases.

Assessment of the response of bone metastases to endocrine or chemotherapy is difficult, and true response rate is probably underestimated by UICC criteria. Biochemical markers of osteoblast activity, which is linked with bone healing, could be useful for early detection of treatment response. We studied changes in osteoblast function, assessed by serial serum total alkaline phosphatase (tALP) at 0, 1, 2, 3 months from the start of systemic therapy, in 31 patients bearing bone metastases from advanced breast cancer. After 1 month of endocrine or cytotoxic treatment, all responding patients (7/31) showed a significant rise in tALP (mean increase: 351 IU/l, p < 0.05) followed by a gradual decrease over the subsequent months (tALP flare). Transient increase in tALP was also found in 2/16 patients with stable disease who benefited from therapy. 2/8 patients with progressive disease showed a rise indistinguishable from responders, but the subsequent decrease was not apparent. These observations suggest that serum tALP profile is an earlier predictor of response than X-rays.