The objective of this phase III trial was to determine the effectiveness of the probiotic formula Probio-Tec® BG-Vcap-6.5 in the prophylaxis of irinotecan-induced diarrhea in metastatic colorectal cancer patients due to a reduction in the activity of intestinal beta-D-glucuronidase. Here, GUSB is linked to metastatic colorectal cancer.