Parallel Alterations in Gut and Tumor Microbiota in Pediatric Oncology: Potential Impacts on Disease Progression and Treatment Response

In the last decade, knowledge of gut microbiota has expanded. Several studies have demonstrated a correlation between certain diseases and alterations in gut microbiota. A comprehensive understanding of this complex ecosystem is still lacking; however, this review highlights the importance of microorganisms in oncology. Recently, several studies have demonstrated that the gut microbiota influences therapeutic efficacy and tumor formation, also known as tumorigenesis. We must remember that these microorganisms also play a crucial role in tumor prognosis. Since the discovery of <i>Fusobacterium nucleatum</i> in colorectal carcinoma (CRC), it has been established that tumor tissues are not sterile and contain microorganisms that can lead to either beneficial or harmful pathways, affecting tumor size and response to chemotherapeutic agents. Additionally, it should be noted that data on the pediatric population are limited, as this area has not been widely researched due to the low number of cases and the complexity of therapeutic approaches. In children, the only available data are mainly based on hematological malignancies, such as acute lymphoblastic leukemia (ALL). For a better understanding, larger cohorts are required.