Background: Little is known about correlations between the growth fraction determined immunohistochemically with Ki-67 antibody and radiation response or prognosis after radiation therapy.
Methods: The prognostic value of the growth fraction determined by Ki-67 index and the mitotic index of proliferating cell population (pMI) were assessed in 45 cervical cancers treated with radiation therapy. The specimens from the cervix before radiation therapy were immunohistochemically stained with anti-Ki-67 antibody.
Results: The mean Ki-67 index and pMI for all patients were 36.0% and 2.74%, respectively. The patients with a Ki-67 index of 33% or greater showed significantly better histologic response to radiation at 30 Gy than those with less than 33%. The mean Ki-67 index for patients with good prognosis was significantly higher than for patients with tumor recurrence or metastasis later. Further, the mean values of pMI for patients with good prognosis were significantly lower than for patients with recurrence or metastasis. The 3-year survival rate for higher Ki-67 index (> or = 33%) was significantly better than lower Ki-67 index (less than 33%) (90.9% versus 34.8%; P < 0.001). However, the 3-year survival rate for higher pMI (> or = 3.5%) was significantly poorer than lower pMI (less than 3.5%) (8.3% versus 81.8%; P < 0.001).
Conclusions: These results suggested that tumors with a high growth fraction showed a good prognosis with radiation therapy. In addition, the inverse prognostic correlation between the Ki-67 index and pMI suggested that both indices have independent values on radiation response and prognosis after radiation therapy.