ACUTE LUMBOSACRAL PLEXOPATHY DURING AND AFTER PREOPERATIVE RADIOTHERAPY OF RECTAL ADENOCARCINOMA

The benefit of preoperative radiotherapy of adenocarcinoma of the rect um with respect to a reduced local recurrence rate and an improved sur vival should be weighed against adverse effects. For 14 years a three- beam, isocentric technique was employed at our hospital to deliver fiv e fractions (5.0 or 5.1 Gy), over 5 or 7 days preoperatively, to patie nts with rectal cancer which was considered primarily resectable. The adverse effects of the radiotherapy were few, but acute pain and subac ute neurological symptoms and signs did occur. An apparent increase in the frequency of these symptoms/signs was noted during 1993. The pain and neurological symptoms are described in case reports and the indiv idual treatments are reviewed. The three-beam technique was analyzed i n detail with individual, CT-based, three-dimensional dose-planning an d dose distributions in the vicinity of the lumbar nerve plexus are pr esented. The major result of this analysis showed that technical error s could be excluded, that human errors were unlikely, and that the cul prit probably was an unexpected sensitivity to marginal changes in the daily dose and unknown or unexpected radiosensitizing effects of conc urrent diseases or medication.