Prognostic significance of grading and staging systems using MIB-1 score in adult patients with soft tissue sarcoma of the extremities and trunk

Background: The predictive value of histologic grading and staging systems for overall survival in different types of adult soft tissue sarcoma of the extremities and trunk is unclear.

Methods: Histologic slides from 193 patients with primary tumors were reviewed for diagnosis, and Ki-67 (MIB-1) immunostaining was performed for grading in all patients. Univariate and multivariate analyses were conducted to analyze the results from patients with soft tissue sarcomas as a group and among the six main histologic categories: malignant fibrous histiocytoma (n = 49 patients), liposarcoma (n = 48 patients), synovial sarcoma (n = 30 patients), spindle cell sarcoma (n = 24 patients), small round cell sarcoma (n = 15 patients), and others (n = 27 patients). The median follow-up was 50 months.

Results: Univariate analysis of soft tissue sarcomas showed that tumor size and depth, histologic type, MIB-1 score, grades based on three criteria (tumor differentiation/histologic type, necrosis, and either mitosis or MIB-1 score) and disease stage, as assessed by tumor size, depth, and grade, were associated with overall survival. Among these variables, grading and staging systems using the MIB-1 score had better predictive value compared with the MIB-1 score and standard grading and staging models in the main histologic categories. Because survival curves for the different tumor grades and stages showed similar trends between the different histologic types, multivariate analysis was conducted adjusting for age, gender, disease site, surgical margin, tumor size and depth, grade, stage, and histologic type. Consequently, Grade 3 emerged as the most significant adverse prognostic factor. Additional adverse prognostic factors were Stage III, Grade 2, a histologic type of spindle cell sarcoma, and patient age > 50 years at the time of presentation. The histologic type liposarcoma was identified as a favorable prognostic factor.

Conclusions: The current results indicate that grading and staging systems using the MIB-1 score are very strong prognostic factors in patients with the main histologic types of soft tissue sarcoma. Specific assessment of histologic type should be carried out before deciding on treatment strategies.