Relative Changes of MIB1 and PC10 Labeling Indexes in Cell Kinetics During Radiotherapy for Cervical Squamous Cell Carcinoma

Abstract

To assess the changes in cell kinetics during radiotherapy (RT) in terms of the MIB1 and PC10 labeling indexes of cancer cells, a total of 230 biopsy specimens taken from 76 consecutive patients with cervical squamous cell carinoma treated with RT was investigated. The MIB1 and PC10 indexes represent the growth fraction and proliferative activity, respectively. The MIB1 index ranged from 11 to 67% (mean value: 38%) before RT, from 21 to 86% (50%) at 5.4 Gy, from 15 to 85% (53%) at 9 Gy, and from 0 to 69% (26%) at 27 Gy. The PC10 index ranged from 4 to 46% (23%) before RT, from 5 to 62% (26%) at 5.4 Gy, from 6 to 63% (23%) at 9 Gy, and from 0 to 35% (11%) at 27 Gy. The correlational relationships between the increment of both indexes during RT (Δ index) and the index before RT were analyzed on an individual basis. The Δ index was calculated by the index at various doses during RT minus the index before RT. Negative linear relationships were observed between the Δ MIB1 index at 9 Gy or Δ MIB1 index at 27 Gy and the MIB1 before RT, and also between the Δ PC10 index at 9 Gy or Δ PC10 index at 27 Gy and the PC10 index before RT. The linear regression coefficient values showed more than 0.5 (0.511 to 0.682) with statistical significance. According to these results, it was suggested that the cervical cancers of lower proliferative activity showed greater increases in growth fraction and proliferative activity by irradiation than those of higher proliferative tumors. These findings suggest that reversal patterns of changes in cell kinetics including growth fraction and proliferative activity took place in the early period of RT for cervical squamous cell carcinomas. The study of changes in cell cycle kinetics in human tumors during RT may have potential impact on the further development of RT.