Analysis of immunohistochemical expression of p53 and the proliferation marker Ki-67 antigen in skull base chordomas: relationships between their expression and prognosis

The prognosis of chordomas is difficult to predict based solely on histological findings. The purpose of this study was to assess the immunohistochemical expression of the proliferation marker Ki-67 antigen and the expression of p53 in skull base chordomas and to relate their expressions to the outcome. We examined the expression of p53 and the MIB-1 labeling index (LI), assessed by Ki-67 expression, in 19 tumors (initial, n = 11; recurrent, n = 8) from 11 patients. The correlation among the MIB-1 LI, p53 expression, and the clinical outcome was analyzed. The mean MIB-1 LI and p53 expression at the initial surgery were 5.6 +/- 4.6% and 9.0 +/- 9.4%, respectively. At the time of recurrence, the mean MIB-1 LI and p53 expression were 10.2 +/- 7.4% and 16.5 +/- 12.0%. The correlation between the MIB-1 LI and p53 expression at the initial and recurrent surgeries was highly significant (r = 0.948; P < 0.0001). The change in p53 expression from the initial to the recurrent chordomas was significantly greater in patients who died of tumor-related causes than in the surviving patients. In the surviving patients, the values for MIB-1 LI and p53 expression in the recurrent tumors were significantly higher in the disease-ongoing group than in the disease-free group. Our results suggest that determination of the immunohistochemical expression of p53 and Ki-67 antigen is helpful to predict tumor recurrence and prognosis in skull base chordomas.