Based on the Ohboshi Shimosato classification, we examined the effects of preoperative chemotherapy on nuclear DNA content and the mitotic index (MI) in oral squamous cell carcinoma, and attempted to correlate them with patients' survival rates.
Ninety patients with oral squamous cell carcinoma treated by preoperative chemotherapy, followed by surgery, participated in this study. Nuclear DNA content and the MI in tissue samples before and after chemotherapy were measured, using a cell image analyzer.
MI decreased in cases that had a decrease in mean nuclear DNA content after chemotherapy. The decreased mean nuclear DNA content is due to inhibition of growth activity of cancer cells by chemotherapeutic agents, resulting in a larger GO/G1 phase fraction, and it is considered to be a favorable response to chemotherapy. On the other hand, cases with an increase in mean DNA content and a decrease in MI were considered to be due to a G2 or S phase fraction increase, caused by inhibition of DNA synthesis, rather than by accumulation of aneuploid cells. These two types of change appeared to have favorable chemotherapeutic effects on cell kinetics.
The five-year cumulative survival rate was 98% for the good response group (Ohoboshi Shimosato classification: grades II b, III, and IV; n=40). The survival data was not significantly different between these groups, classified according to chemotherapeutic effects on cell kinetics. The five-year cumulative survival rate was 58% for the poor response group (grades I, II a; n=50): 61% for 16 patients with a decrease in mean DNA content, 81% for 18 patients with an increase in mean DNA content and a decrease in MI, and 31% for the remaining 16 patients, who failed to obtain sufficient chemotherapeutic effects on cell kinetics. The survival rate of the latter 16 patients was significantly poor compared with the former two groups.
From these results, it was suggested that this type of analysis was useful for the prognosis of patients with oral squamous cell carcinoma treated by preoperative chemotherapy followed by surgery, and that it offered a unique opportunity to flexibly adjust the modalities of adjuvant therapy.
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