Clinical Significance of P-Glycoprotein Immunohistochemistry and Histomorphologic Factors in Patients with Osteosarcoma

Background: Osteosarcoma is the most frequent highly malignant bone tumor with a peak incidence in the second decade of life. Although survival rate increased up to 60-70% within the last 10 years, the problem of unresponsiveness to chemotherapy remains. In this study, we sought to determine the prognostic significance of P-glycoprotein as a tumor marker for osteosarcoma. Methods: In a retrospective study, we correlated P-glycoprotein immunostaining with clinicopathologic and histomorphologic features of the tumor and the patient outcome in 30 cases with primary, non-metastatic, highgrade osteosarcoma who were homogeneously treated. Results: P-glycoprotein positivity was found in 14 of 30 cases and was significantly associated with a higher incidence of adverse events and relapse rate. No relationship was found between p-glycoprotein immunostaining and clinicopathologic features such as age, sex, tumor site, histologic subtype, osteoid content, osteoid pattern, pretreatment necrosis, pleomorphism of the cells, and presence of prominent nucleoli, except for mitotic activity per 10 HPF. Conclusions: P-glycoprotein positivity in immunohistochemistry should be taken into consideration to identify a subgroup of osteosarcoma patients with poor outcome at the time of diagnosis. So it might be an important marker in planning innovative chemotherapeutic regimens.