Patients at both MSKCC and Regensburg had a better chance of overall survival if they had high intestinal microbial diversity around the period of neutrophil engraftment, as seen in a sample collected within 7 days of post-HCT day 14. At MSKCC, data for 651 patients showed a statistically significant association (P = .006); this finding was reproduced at Regensburg, which also saw a significant association (P = .015) for the 59 patients studied, Dr. Peled reported.
Increased treatment-related mortality was seen for patients who had low microbial diversity following neutrophil engraftment as well. Of 372 MSKCC patients who had samples available 7-50 days after engraftment, high diversity was associated with better overall survival, and with lower treatment-related mortality (P = .03 for both).
Dr. Peled and his collaborators also divided patients into quartiles by amount of biodiversity. They found that comparing the highest to the lowest biodiversity quartile showed significantly overall survival benefits for the highest-diversity group (P = .007).
The problem starts before transplant, Dr. Peled explained. The researchers found that compared with healthy controls at MSKCC and data from the Human Microbiome Project, HCT patients entered their transplant with significantly less gut biodiversity.