Could a gut bacteria transplant help when immunotherapy stops working for stomach cancer?

When immunotherapy stops working for advanced stomach or colon cancer, patients often have few options left. This small, early-stage study tested a new idea: what if we could 'reset' a patient's gut bacteria to help their immune system fight back? Ten patients whose cancers had become resistant to standard immunotherapy received a transplant of healthy donor gut bacteria, taken in capsule form, alongside continued immunotherapy treatment. The most important finding was that this combination was safe, with no serious side effects reported. In terms of early results, two out of the ten patients (20%) saw their tumors shrink, and four patients (40%) had their disease stop growing for a period. The researchers saw that patients who benefited seemed to have new, helpful bacteria from the donor take hold in their gut, and their blood showed signs of a more active immune system. They also identified specific patterns of gut bacteria linked to a better response to treatment. This is just a first step, but it shows that combining a gut bacteria transplant with immunotherapy is a safe and feasible path to explore for patients who have otherwise run out of effective treatments.