Histological Effects and Local Control of Preoperative High-dose Radiotherapy for Rectal Cancer

High dose preoperative pelvic radiation (60 Gy) was performed on 36 patients with rectal adenocarcinoma and local effects was evaluated histologically. Macroscopically, the size of the main tumor reduced 23 % (median) subsequent to the irradiation. Histologically a variety of change of cancer cells were observed, and the effects were graded into 5 grades, low, moderate and high I, II, III (no remnant cancer cells) grades. The percentage of the number of the patients showing each grade were as follows: low (5.9 %), moderate (41.2 %), high I (41.2 %), II (5.9 %), III (5.9 %). Generally, histological effects were most prominent at the deepest part of the cancer. Thus in 50 % of irradiated cases safer external surgical margin was achieved. The preoperative radiotherapy were also effective on vascular involvement at the main growth and lymphnode metastasis as well. The incidence of local recurrence was less than controls and 2-3 year in irradiated cases survival rats were improved so far.