[Prevention of radiation-induced diarrhea by smectite. Results of a double-blind randomized, placebo-controlled...

Diarrhea and abdominal pain are well-known side effects abdominal or pelvic of radiation therapy that may lead to interruption of treatment in serious cases. In recent trials the silicate smectite has proven a promising drug in the prophylaxis of these adverse events. The presented trial aimed at the verification of earlier studies and the evaluation of a dose-effect relationship.

Between April 1994 and May 1995, a total of 176 patients obtaining radiotherapy of the pelvis or the abdomen were evaluated in a double-blind, randomized placebo-controlled investigation regarding the prophylactic effect of smectite (= Colina) against radiotherapy-induced diarrhea. During the whole period of radiotherapy 85 patients obtained 2 x 6 g smectite daily and 91 patients received 2 x 6 g placebo. The primary end point of the analysis was the time to the first appearance of diarrhea (> or = 3 pappy stools).

All 176 patients were evaluated according to an intent-to-treat analysis. There was no significant difference between the prophylactic effects of smectite and placebo. For an explorative post-hoc analysis the total study group was split up into 2 subgroups, one with an irradiated small bowel volume < or = 837.5 ml, the other with a small bowel volume > 837.5 ml (median); the analysis indicated that the first subgroup showed a benefit for the smectite-treated patients in contrast to the placebo treatment (32 vs. 18 calendar days to the first appearance of diarrhea). This benefit was statistically not significant.

Prophylactic application of smectite during irradiation of the pelvis and the abdomen can delay the development of radiotherapy-induced diarrhea, a statistical significance could not be verified neither in the total study group nor in the post-hoc subgroup analysis.