20 patients with rectal cancer within 8 cm of the anal verge were studied. Endoscopic endosonography was carried out before and after pre-operative radiotherapy (45 Gy over three weeks). The local extent (tumour stage and diameter) was compared with the results of his topathological examination of the resected specimen after anterior resection  or total rectal excision . The Tumour Regression Grade (TRG) and lymph node status were also estimated. Two patients were not evaluated endosonographically. Two (11%) of the remaining 18 patients showed ultrasound evidence of down staging (14/18 uT3/4 pre-radiotherapy: 12/18 uT3/4 after) and tumour diameter was significantly reduced. Tumour Regression Grade estimation showed evidence of response to treatment, showing regression of more than 50% in 13 (65%) of cases. Involved nodes were less than 5 mm in diameter in 45% of cases. Histopathological evidence of nodal metastatic regression was seen in 13 (28%) of all involved nodes found. The ultrasonically determined response to radiotherapy may offer useful information in predicting outcome and possibly in selecting surgery.
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