Transplanted Gut Bacteria Could Boost or Block Cancer Treatment

Fecal microbiota transplantation can enhance or hinder immunotherapy depending on factors like donor, patient, and bacterial composition.

Fecal microbiota transplantation (FMT) shows both encouraging potential and significant challenges in boosting the effectiveness of cancer immunotherapy, particularly immune checkpoint inhibitors ().

A comprehensive review published in Gut Microbes highlights the controversial and inconsistent outcomes of transferring healthy gut bacteria into cancer patients undergoing these treatments.

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Some cancer patients who failed immunotherapy, 40% responded again after receiving gut bacteria from healthy donors—but in others, the same treatment made things worse. #medindia #gutmicrobiome #cancerimmunotherapy

Variable Effects on Immune Checkpoint Inhibitors

"FMT's impact on immune checkpoint inhibitor efficacy varies dramatically across studies," explains lead researcher Dr. Peng Luo from Southern Medical University. "Some clinical trials show remarkable improvements in patient outcomes, while others demonstrate no benefit or even potential harm."

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Outcomes Across Cancer Types

The research team analyzed multiple clinical trials involving melanoma, colorectal cancer, and other solid tumors. In some melanoma studies, 40% of patients who previously failed immunotherapy showed renewed responses after FMT. However, other trials found that certain bacterial formulations actually reduced treatment effectiveness compared to placebo.

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Role of Gut Microbiome as an Ecosystem

"The gut microbiome acts like a complex ecosystem that can either support or hinder the immune system's ability to fight cancer," notes Dr. Luo. "We discovered that the success of FMT depends on multiple factors including donor selection, recipient characteristics, and the specific bacterial communities being transferred."

The review identifies key mechanisms by which gut bacteria influence cancer treatment. Beneficial bacteria can enhance immune cell function and alter the tumor microenvironment, while harmful bacteria may promote immunosuppressive cells that protect tumors from attack.

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Personalized Response to Bacterial Species

"What surprised us most was how the same bacterial species could have opposite effects in different patients," Dr. Luo explains. "This highlights the need for personalized approaches rather than one-size-fits-all treatments."

The researchers emphasize that large-scale clinical trials are urgently needed to clarify FMT's role in cancer therapy. They also call for standardized protocols and better methods to predict which patients will benefit from microbiome interventions.

Reference:

From chaos to order: optimizing fecal microbiota transplantation for enhanced immune checkpoint inhibitors efficacy - (https://www.tandfonline.com/doi/full/10.1080/19490976.2025.2452277)

Source-Eurekalert