A phase II, randomized, double blind comparison of calcium aluminosilicate clay (CASAD) versus placebo (dibasic calcium carbonate) for the prevention of diarrhea in patients (pts) with metastatic colorectal cancer (mCRC) treated with irinotecan (I).

3600 Background: CASAD is a naturally occurring calcium montmorrilonite clay that serves as a cation exchange absorbent. One of the active metabolites of Irinotecan is SN-38, which is adsorbed by CASAD in vitro. The study hypothesis was that oral CASAD would reduce the rate of grade 3/4 diarrhea in mCRC patients treated with irinotecan. Methods: The study is a multicenter, prospective, randomized, double blinded placebo-controlled phase II trial. One hundred patients receiving I-based chemotherapy were randomized equally between CASAD (1000 mg po 4x daily) and placebo in order to have 75% power to detect a difference in the proportions of patients with grade 3/4 diarrhea within 6 weeks at a 1-sided 5% significance level. We also compared symptom burden using the MDASI questionnaire summed over the 13 symptom items for weeks 0, 3, 5, and 6. Results: Between 5/2009 and 5/2012, 100 patients were randomized in a 1:1 ratio between study arms. Median age 57 yrs, 54% male, 74% Non-Hispanic White, 93% performance...