PREOPERATIVE RADIOTHERAPY FOR RESECTABLE CANCER OF THE MIDDLE-DISTAL RECTUM - ITS EFFECT ON THE PRIMARY LESION AS DETERMINED BY ENDORECTAL ULTRASOUND USING FLEXIBLE ECHO COLONOSCOPE

20 patients with rectal cancer within 8 cm of the anal verge were stud ied. Endoscopic endosonography was carried out before and after pre-op erative radiotherapy (45 Gy over three weeks). The local extent (tumou r stage and diameter) was compared with the results of histopathologic al examination of the resected specimen after anterior resection [12] or total rectal excision [8]. The Tumour Regression Grade (TRG) and ly mph node status were also estimated. Two patients were not evaluated e ndosonographically. Two (11%) of the remaining 18 patients showed ultr asound evidence of down staging (14/18 uT3/4 pre-radiotherapy: 12/18 u T3/4 after) and tumour diameter was significantly reduced. Tumour Regr ession Grade estimation showed evidence of response to treatment, show ing regression of more than 50% in 13 (65%) of cases. Involved nodes w ere less than 5 mm in diameter in 45% of cases. Histopathological evid ence of nodal metastatic regression was seen in 13 (28%) of all involv ed nodes found. The ultrasonically determined response to radiotherapy may offer useful information in predicting outcome and possibly in se lecting surgery.