The role of intestinal microbiota in colorectal and breast cancer treatment: a pathway to personalised medicine?

Colorectal and breast cancer are common cancers worldwide. Classical chemotherapeutics remain the systemic backbone of cancer treatments here. However, chemotherapeutics have side effects and tumour response can be optimized. Pre-clinical studies have indicated that intestinal microbiota (bacteria) might be involved in the development of cancer and influence cancer treatment efficacy and side effects. However, limited clinical studies are available. This doctoral study examined the role of intestinal microbiota in colorectal and breast cancer and cancer treatment specifically. It was concluded that in patients with metastatic colorectal cancer the intestinal microbiota did not change during chemotherapy treatment with capecitabine. In addition, baseline intestinal microbiota composition could not predict tumour response in metastatic colorectal cancer patients. In postmenopausal hormone positive breast cancer patients the intestinal microbiota changed during the course of chemotherapy treatment with adriamycin, cyclophosphamide, and docetaxel. Postmenopausal women with or without breast cancer could not be differentiated based on the intestinal microbiota composition