The effect of hyperthermia and radiation on small bowel permeability using 51Cr EDTA and 14C mannitol in man.

A prospective study was conducted to study the effect of radiotherapy (RT) and regional pelvic hyperthermia (HT) on intestinal permeability in three groups of patients. Fifteen acted as cancer controls, receiving RT away from the peritoneal cavity, 21 patients received radical pelvic or abdominopelvic RT and 13 patients pelvic RT followed by pelvic HT using a BSD 1000 phased array applicator. Small bowel permeability was measured by oral administration of a mixture of [51Cr]EDTA, [14C]mannitol and lactulose before and after a course of treatment. The absorption of each marker was calculated by measuring the urinary excretion over 0-6 and 0-12 hours. The 6 hour collection gave results similar to the 12 hour collection, but had logistical advantages. The EDTA absorption rose and the mannitol absorption fell during a course of treatment, but the best index of permeability change was the EDTA/mannitol ratio (E/M). The E/M ratio rose by a factor of 2.4 (P less than 0.001) and 1.82 (P = 0.05) following RT and RT/HT respectively. There was no significant difference between the RT and RT/HT groups but the thermal dose to the RT/HT group was low (23 min./equiv 43 degrees C over three or four fractions in 4 weeks). There was no correlation between small bowel permeability and bowel frequency. The E/M permeability test is a useful simple functional assay for assessing small bowel damage after RT and RT/HT.