Background: In osteosarcoma the histological response, measured by the percentage of tumor necrosis, constitutes one of the most significant predictive factors, with better survival in patients whose tumor necrosis is > or = 90%.
Objectives: To determine if the decrease rate of serum alkaline phosphatase (SAP) levels during the first month of neoadjuvant chemotherapy could serve as a predictive indicator of tumor necrosis and clinical outcome.
Methods: We analyzed the medical files of 53 osteosarcoma patients (19 females, 34 males) (median age 16 years, range 8-24); the disease was metastatic in 12 and localized in the other 41.
Results: The histological responses were good in 38 patients (71.7%) and poor in 15 (28.3%). At a median follow-up of 50 months, 34 patients (64.2%) had no evidence of disease and 19 (35.8%) had died from the disease. High levels of SAP at diagnosis correlated with worse survival (P = 0.002). There was no difference in overall survival between patients whose SAP decrease rate was > 25% and those with a rate < 25% (P = 0.14). Among female patients, "rapid" SAP responders had better survival than "slow" responders (P= 0.026). In patients with metastases the SAP decrease rate was positively correlated with survival (P = 0.042).
Conclusions: There was no evidence that "rapid" SAP responders had a higher percentage of tumor necrosis than "slow" responders, although female "rapid" SAP responders had a better prognosis than "slow" responders. Patients with metastases at presentation and "rapid" SAP response had better prognoses.