OBJECTIVETo investigate the effect of preoperative radiotherapy as an adjunctive approach on proliferation and apoptosis of cancer cells in rectal cancer.

METHODSEighty patients with (p)TNM stage II or III rectal cancer were enrolled from April 2000 to December 2002. The patients were divided into two groups, which were group received surgical treatment alone (40 cases) and group received preoperative adjuvant radiotherapy with a radiological dose of 40 G( y ) (40 cases). The expression of Ki- 67 protein in rectal cancer was detected immunohistochemically and apoptosis was detected by TUNEL technique.

RESULTSIn radiotherapy group, the tumor volume shrank markedly in 14 cases, partially in 18,slightly in 8 with an overall efficiency rate of 80% .There was significant positive correlation between spontaneous apoptosis and Ki- 69 marker index in cancer tissues before radiotherapy(gamma =0.563P=0.027). The expression of Ki- 67 in rectal cancer tissues was significantly lower after radiotherapy than that before radiotherapy, as well as in the control group(P=0.017 vs. P=0.011).The expression of Ki- 67 in paratumor tissues 2cm from tumor was significantly lower after radiotherapy than that before radiotherapy. Apoptosis index (AI) in rectal cancer tissues was significantly higher after radiotherapy than that before radiotherapy, and that in the control group (P=0.013 vs. P=0.018).

CONCLUSIONRadiotherapy can inhibit proliferation and induce apoptosis of rectal cancer cells. The expression level of Ki- 67 can be considered as a screening index for preoperative radiotherapy.