Abstract
OBJECTIVES: Dysfunctional processing of fear memory may be involved in the pathophysiology of fear of cancer recurrence (FCR), which is cited as the major unmet psychological need of cancer survivors. Emerging evidence has shown that the microbiota-gut-brain (MGB) axis affects psychiatric disorders, including depressive and anxiety disorders, which are associated with fear memory (PMID: 29628046). We therefore hypothesized that the gut microbiota is associated with FCR in cancer survivors (PMID: 29628046). METHODS: This cross-sectional study enrolled women diagnosed with invasive breast cancer who were not currently undergoing chemotherapy. Fecal samples were obtained to assess the gut microbiota. FCR grade was assessed using the Concerns About Recurrence Scale (CARS). RESULTS: Mean age of the participants (n = 126) was 58 years; 47% had stage I disease. Multiple regression analysis with adjustment for possible confounders showed that the relative abundance of the Bacteroides genus (beta = 0.180, P = 0.03) was significantly and directly associated with FCR. In the 57 participants with a history of chemotherapy, higher FCR was associated with lower microbial diversity (P = 0.04), lower relative abundance of Firmicutes (P = 0.03) and higher relative abundance of Bacteroidetes (P = 0.04) at the phylum level, and higher relative abundance of Bacteroides (P < 0.01) and lower relative abundance of Lachnospiraceae.g (P = 0.03) and Ruminococcus (P = 0.02) at the genus level. CONCLUSIONS: Our findings provide the first evidence of an association between the gut microbiota and FCR and suggest that chemotherapy-induced changes in gut microbiota can influence FCR. Further studies should examine the effects of the gut microbiota on FCR using a prospective design. FUNDING SOURCES: This study was supported in-part by a donation from Morinaga Milk Industry Co. Ltd, grants from the Japan Society for the Promotion of Sciences and the Foundation for Promotion of Cancer Research.