Here is some earlier (cited) work in mice that very strongly showed an effect between this therapy and the mouse gut microbiome (Commensal Bifidobacterium promotes antitumor immunity and facilitates anti–PD-L1 efficacy): http://science.sciencemag.org/content/early/2015/11/04/scien.... Really interesting to see these finding preliminarily reproduced in a clinical setting.
Theory/ educated guess: these therapies try to antagonize the PD1 receptor, which is found on immune cells (specifically, T cells); in a healthy individual, the binding of PD-1L to PD-1 provides a "don't kill me" signal so that the body's own cells are not destroyed by the immune system.
The problem with this is that cancers frequently develop mutations and overexpress PD-1L which prevents the immune system from properly targeting them for destruction. These anti-PD1/ anti-PD1L try to counteract this overexpression, allowing the immune system's T cells to destroy the cancer.
However, targeting the cancer requires a functional immune system; this is where the gut microbiome comes in. It's a sort of "home gym" for the immune system--having a diverse range of bacteria helps keep the immune system strong; gnotobiotic mice (mice bred and raised in completely germ-free environment without any gut microbes) have significantly weakened immune systems.
So theory is that the gut microbiome acts as a "home gym" where the immune system can "train". Anything that reduces gut microbiome (such as antibiotics) will also reduce this "training" and leave the immune system less able to apply its training to fighting off cancer cells.
One of the things that came up at a recent kidney cancer seminar I attended, is that they are seeing better immune response with a more diverse gut biome.
The University of Washington researchers weren't willing to give medical advice, but they were very pro- immune treatment patients taking probiotics. They are still a few years out from publishing.
I was privileged to get to sysadmin for a pioneer microbiologist-geneticist whose passion was the microbiome. Not long before I left, I started seeing indicators that the the microbiome(s) in us and that we encounter and how they interact is vastly more important than we have realized. From this biofilms have made advances, etc. With sequencing getting so much cheaper, the research opportunities are just sitting around waiting, and are the kind that offer real and tangible results.
Beans are the best, as they have the highest percentage of fermentable fiber in the form of raffinose. Pectin in apples, pears and citrus, the beta-glucan in oats and barley, and inulin in alliums, chicory and jerusalem artichoke are all good as well.
To get the most benefit, pair your fiber source with a probiotic food. Good examples are unpasteurized sauerkraut, kimchi, yogurt, kefir, etc.
- Gut microbiome modulates response to anti–PD-1 immunotherapy in melanoma patients http://science.sciencemag.org/content/early/2017/11/01/scien...
- Gut microbiome influences efficacy of PD-1–based immunotherapy against epithelial tumors http://science.sciencemag.org/content/early/2017/11/01/scien...
Here is some earlier (cited) work in mice that very strongly showed an effect between this therapy and the mouse gut microbiome (Commensal Bifidobacterium promotes antitumor immunity and facilitates anti–PD-L1 efficacy): http://science.sciencemag.org/content/early/2015/11/04/scien.... Really interesting to see these finding preliminarily reproduced in a clinical setting.