Expression of MIB-1, mitotic index and S-phase fraction as indicators of cell proliferation in superficial bladder cancer. Finnbladder Group.

Cell proliferation of transitional cell bladder cancer (TCC) was determined by MIB-1 immunolabeling, volume-corrected mitotic index (M/V index) and S-phase fraction measurement in 207 patients with superficial (Ta-T1) bladder cancer. The results were compared to T category, WHO grade and DNA-ploidy. The MIB-1 score was related to T category (P < 0.001), WHO grade (P < 0.001), DNA ploidy (P < 0,0001), M/V index (P < 0.0001) and fraction of cells in S phase (P < 0.0001). The mean MIB-1 score was 6.37% for G1, 14.59% for G2 and 28.59% for G3 carcinomas (P < 0.001). The MIB-1 score for Ta tumors was 9.24% and for T1 tumors 25.34% (P < 0.001). The M/V index was 3.9 for G1, 11.5 for G2 and 25.9 for G3 tumors (P < 0.0001). The M/V index for Ta tumors was 6.4 and 25.3 for T1 tumors (P < 0.0001). WHO grade 1 tumors had 7.7%, grade 2 tumors 13.8% and grade 3 tumors 21.8% of cells in S phase (P < 0.001). Of grade 1 tumors, 97% were diploid and 3% aneuploid, and 78% of grade 2 tumors were diploid and 22% aneuploid. Of grade 3 tumors, 30% were diploid and 70% aneuploid (P < 0.001). Of Ta tumors, 92% were diploid and 8% aneuploid, respectively, whereas 40% of T1 tumors were diploid and 60% aneuploid (P < 0.0001). The results show that quantitative cell proliferation indices are associated with T category and WHO grade in superficial bladder cancer. The prognostic value of the S-phase fraction and mitotic index has been demonstrated in several previous analyses of prognostic factors while the value of MIB-1 score on bladder cancer prognosis remains to be established in further follow-up studies.