Microbiotic Product to Promote Microbiome Health and Improve Chemotherapy Delivery

This study tests whether a probiotic (beneficial bacteria) supplement can improve the health of gut bacteria and reduce the severe diarrhea that commonly occurs with irinotecan chemotherapy in people with metastatic colon cancer. **You may be eligible if...** - You have been diagnosed with metastatic colon cancer confirmed by biopsy - You are scheduled to receive irinotecan-based chemotherapy (second-line or later) - Your overall health is good (performance status 0–1) - Your blood counts, kidney, and liver function are within acceptable ranges - If you previously received irinotecan, you have been off it for at least 3 months and your bowel habits have returned to normal **You may NOT be eligible if...** - You currently have moderate to severe diarrhea (more than 4–6 extra bowel movements per day above your normal) - You are unable to take oral supplements - You are currently on antibiotic therapy - You have a known genetic variant that affects irinotecan metabolism (UGT1A1) Talk to your doctor to see if this trial is right for you.