Prognostic relevance of a histological grading system using MIB-1 for adult soft-tissue sarcoma

Several histological grading systems have been proposed and found as strong indicators of outcome in soft-tissue sarcomas. However, a putative independent prognostic influence of recently developed biological and molecular markers remains to be established. This study investigated the prognostic relevance of a histological grading system based on the assessment of proliferative activity in adult soft-tissue sarcomas of the extremities, trunk, head, and neck. Tissue blocks from 95 of 108 patients without distant metastases or regional lymph node involvement were available. Immunohistochemical staining for MIB-1 and p53 was done on paraffin-embedded sections. All clinicopathologic and immunohistochemical variables and patient survival were assessed using univariate and multivariate analyses. Variables included histological grading based on the modified Fédération Nationale des Centres de Lutte Contre le Cancer (FNCLCC) system using the MIB-1 score for the estimation of the proliferative potential of the tumors. Variables associated with overall survival were tumor site in the trunk, head and neck, mitosis count, necrosis, MIB-1 score, FNCLCC grade, modified FNCLCC grade using the MIB-1 score, and stage (all p values <0.05). In multivariate analysis, the modified grade proved to be the most significant predictor of shortened overall survival, in addition to tumor site in the trunk, head, and neck. Overexpression of p53 did not correlate with increased risk of tumor mortality. Using MIB-1 to replace mitosis counts in the FNCLCC system improves grading of soft-tissue sarcomas, and this in conjunction with other important factors appear to be more accurate prognostic factors for survival, and for patient selection in investigational adjuvant treatment trials.