Does Gut Flora Impact the Response to Cancer Immunotherapy? Modulating the microbiome could boost therapy, studies suggest

Gut microbes can help or hinder cancer patients' response to immunotherapy, two new studies suggested. In 112 melanoma patients undergoing anti-PD-1 immunotherapy, those with a high diversity of gut microbes had not yet reached median progression-free survival (PFS) after nearly 2 years, because less than half of them had progressed, while median PFS in the low-diversity group was 188 days (hazard ratio 3.57, 95% CI 1.02-12.52, P<0.05), said Jennifer Wargo, MD, of the MD Anderson Cancer Center in Houston, and colleagues. Patients with more bacteria of the Ruminococcaceae family and Clostridiales order in their gut, and especially of the genus Faecalibacterium, had significantly longer median PFS compared with patients with less of these bacteria (median not reached vs 242 days, P<0.05). However, patients with more bacteria of the Bacteroidales order had significantly reduced median PFS compared to those with less (188 days vs 393 days, P<0.05), Wargo's group reported online in Science. Patients with a higher abundance of Clostridiales/Ruminococcaceae bacteria had greater T cell penetration into tumors and higher levels of circulating CD4+ and CD8+ T cells with a preserved cytokine response to anti-PD-1 therapy. However, patients with abundant Bacteriodales had higher levels of circulating regulatory T cells, myeloid derived suppressor cells, and a blunted cytokine response, resulting in dampening of anti-tumor immunity, the authors found. https://www.medpagetoday.com/hematologyoncology/myeloma/69098?xid=NL_breakingnews_2017-11-07&eun=g721819d0r&utm_source=Sailthru&utm_medium=email&utm_campaign=MorningBreak_110717&utm_term=Morning%20Break%20-%20Active%20Users%20-%20180%20days