GDF15 is well known to be an inflammatory marker, but the causality or association with diarrhea is difficult to assess, especially since diarrhea is a known toxicity of many cancer-directed therapies, but knowing that GDF15 is released from tissue injury, more temporal examination of GDF15 levels in times of mucositis, acute diarrhea, or dehydration would be key to understanding the relationship with other gastrointestinal symptoms. The gene discussed is GDF15; the disease is cancer.