Dietary fibre and probiotics impact gut bacteria and immunotherapy responses in melanoma patients, a new study in patients shows. A high-fibre diet was associated with improved survival and response to immunotherapy, the results reveal.

The influence of the gut microbiome on therapeutic response has now been demonstrated in numerous human cohorts and in preclinical models. The human gut microbiome is shaped by a wide variety of environmental exposures, including diet and medication use.

But whether factors such as dietary fibre intake and the use of commercially available probiotics affect immunotherapy responses in cancer patients remains unclear.

To understand how dietary habits impact microbiota and clinical outcomes to immunotherapy, Christine Spencer et al. performed an observational study that began with analyzing the gut microbiome profiles of 438 melanoma patients.

The majority of these patients (87%) received immune checkpoint blockade (ICB) therapy. As they began therapy, the patients were asked to complete a lifestyle survey of usage of antibiotics and probiotics, as well as a dietary questionnaire.

Among those who completed the survey and questionnaire, the authors found no significant difference in outcomes in progression-free survival for patients who did take probiotics, versus those who did not. They next sought to assess the effect of dietary fibre intake on response to ICB.

The patients with sufficient fibre intake had improved survival compared to the patients with insufficient fibre intake.

After this, the authors evaluated whether dietary fibre intake and probiotic use may jointly affect clinical outcomes. The most marked benefit was observed for patients reporting a combination of high fibre consumption and no use of over-the-counter probiotic supplements.

Further work in preclinical models supported the authors’ hypothesis that dietary fibre and probiotics modulate the microbiome and that antitumour immunity is impaired in mice receiving a low-fibre diet and in those receiving probiotics.

Ongoing dietary intervention studies in the setting of immune checkpoint blockade therapy are critical for establishing whether a targeted and achievable diet change at the initiation of therapy can safely and effectively improve outcomes, the authors say.

Source: American Association for the Advancement of Science/AAAS