Prophylaxis of irradiation-induced diarrhea with smectite. Results of a placebo-controlled investigation

Purpose: Diarrhea and abdominal pain are well-known side effects abdominal or pelvic of radiation therapy that may lead to interruption of treatment i n serious cases. In recent trials the silicate smectite has proven a promis ing drug in the prophylaxis of these adverse events. The presented trial ai med at the verification of earlier studies and the evaluation of a dose-eff ect relationship. Patients and Methods: Between April 1994 and May 1995, a total of 176 patie nts obtaining radiotherapy of the pelvis or the abdomen were evaluated in a double-blind, randomized placebo-controlled investigation regarding the pr ophylactic effect of smectite (= Colina(R)) against radiotherapy-induced di arrhea. 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 (gre ater than or equal to 3 pappy stools). Results: All 176 patients were evaluated according to an intent-to-treat an alysis. There was no significant difference between the prophylactic effect s of smectite and placebo. For an explorative post-hoc analysis the total s tudy group was split up into 2 subgroups, one with an irradiated small bowe l volume less than or equal to 837.5 mi, the other with a small bowel volum e > 837.5 mi (median); the analysis indicated that the first subgroup showe d a benefit for the smectite-treated patients in contrast to the placebo tr eatment (32 vs. 18 calendar days to the first appearance of diarrhea). This benefit was statistically not significant. Conclusion: Prophylactic application of smectite during irradiation of the pelvis and the abdomen can delay the development of radiotherapy-induced di arrhea. a statistical significance could not be verified neither in the tot al study group nor in the post-hoc subgroup analysis.