Immune checkpoint inhibitors (ICIs) have become a promising new treatment for advanced cancers, including melanoma. Immunotherapies, including ICIs, target a patient’s immune system to increase its ability to fight cancer as opposed to directly attacking cancer cells like traditional cancer therapies such as chemotherapy and radiation. While the ability of ICIs to improve survival for cancer patients is often profound, they remain effective only on a subset of patients. Thus, researchers actively seek new strategies for increasing the population of patients who respond to ICIs. A new manuscript published late last month in Science has uncovered a potential method for boosting the efficacy of immunotherapy: a high fiber diet.
Gut microbiota influences how well an individual will respond to ICI therapy. Diet and supplement use directly impact the composition of the bacteria present in the gut, but whether diet plays a role in ICI efficacy is not well understood. The researchers addressed the relationship between diet and ICI response in a large cohort of melanoma patients. They found that patients with a high dietary fiber intake exhibited significantly better overall survival.
The study profiled the microbiota of each patient and collected data on dietary habits and supplement use. Assessment of diet was based on patient-reported data. All patients in the study received ICI to treat melanoma.
About 30% of the 128 patients reported sufficient dietary fiber intake. The patients reporting insufficient dietary fiber intake demonstrated an average progression-free survival time of 13 months. The patients reporting sufficient dietary fiber intake had not yet reached average progression-free survival at the time of publication. Further analysis revealed that every 5-gram increase in daily dietary fiber intake corresponded with a 30% reduction in risk of melanoma progression.
The researchers utilized a mouse model of melanoma generated using M3 melanoma cells to mimic the findings in a pre-clinical model. Tumor-bearing mice were treated with ICI while consuming a high- or low-fiber diet. In line with the clinical analysis, mice receiving a high fiber diet and ICI had significantly delayed tumor growth.
The study combined clinical and pre-clinical analyses to demonstrate a link between fiber intake and ICI response. Collectively, the data support an essential role of dietary fiber that should be considered for patients receiving ICI therapy. Further investigation is warranted to evaluate the full impact of fiber intake for cancer patients, particularly those receiving immunotherapy. ICIs have revolutionized the treatment of several types of cancer including melanoma, but the number of patients who do not respond remains disappointing. This study presents a new strategy that could be used to increase the number of responders.