The predictive role of Ki-67 protein in determining the aggressiveness of primary malignant bone tumors. A retrospective study

Introduction: In order to diagnose and stage malignant bone tumors, the pathologic examination of harvested pieces with immunohistochemistry test is necessary; they also provide information regarding the prognosis on a medium to long term. Among tissular biomarkers with potential predictive value, a raised Ki-67 protein level is used to determine the risk of local recurrence or metastasis.

Material and method: This study was performed on 50 patients with primary malignant bone tumors admitted in the Traumatology and Orthopedy Department of University Emergency Hospital, Bucharest. Patients repartition according to diagnosis was the following: 21 patients with osteosarcoma, 18 patients with chondrosarcoma, 6 patients with Ewing sarcoma, 3 patients with malignant fibrous histiocytoma, and 2 with fibrosarcoma. The follow-up period was between 12 and 72 months with a mean of 26 months.

Results: Patients were aged between 18 and 77 years old, with a mean age of 41,36. There were 22 women and 28 men. No sex or age difference was notable for the tumor outcome. After calculating the Ki-67 LI, 36 patients were included in the high-risk group (Ki-67 LI > 25%), while 14 had a low risk for metastasis and local relapse (Ki-67 < 25%). The low-risk patients had chondrosarcoma (8 patients), osteosarcoma (5 patients), and fibrosarcoma (1 patient). During the follow-up, 8 patients, all belonging to the high risk group, developed metastasis, while 5 patients developed local recurrences; 4 patients who relapsed belonged to the high risk group and 1 to the low risk group. Metastases developed in 3 patients with osteosarcoma, 2 with Ewing sarcoma, 2 with chondrosarcoma and 1 patient with fibrosarcoma. Most metastases occurred within one year after surgery. The other fibrosarcoma patient developed local recurrence after 6 months, while the other local recurrences occurred in osteosarcoma patients (2 cases) and 1 in a Ewing sarcoma patient and chondrosarcoma patient.

Conclusions: Our study concluded that while Ki-67 LI values are useful in determining the aggressivity of primary malignant bone tumors, it should always be used in conjunction with the clinical, imaging and anatomopathological diagnosis methods in order to accurately predict the patients’ outcome.