Background: It is known that many patients with osteosarcoma have high serum alkaline phosphatase (SAP) levels. The prognostic significance of this finding, however, is still controversial.
Methods: The pretreatment SAP levels of 656 patients with osteosarcoma of the extremities (107 metastatic and 549 localized at presentation) were examined to evaluate whether the enzyme levels had a clinical value in predicting the course of the disease.
Results: The percentage of patients with increased SAP levels was significantly higher in the metastatic group than in the group of patients with localized disease (91.5% versus 61.3%; P < 0.001). In the latter group, treated with adjuvant and neoadjuvant chemotherapy, the relapse rate was significantly higher in patients with elevated pretreatment SAP levels than in those with normal levels (55.1% versus 26.4%; P < 0.001). Among patients with elevated SAP levels, the percentage of relapses was higher in patients with high levels of the enzyme in comparison with patients with moderately elevated values (66.4% versus 47%; P < 0.05). After treatment, SAP levels almost always return to normal values, and a correlation between postoperative levels of the enzyme and prognosis could not be made.
Conclusions: These data demonstrate that in osteosarcoma of the extremities, pretreatment SAP levels have a prognostic value and they should be considered when comparing the results achieved with different therapeutic protocols and in planning new randomized clinical trials.