This review examines how nutrition and food-based interventions can improve cancer treatment outcomes for patients receiving targeted cancer therapies. A Mediterranean-style diet with plenty of fiber (30-50g daily) appears beneficial for patients on immune checkpoint inhibitor therapies by promoting healthy gut bacteria that support immune function. The review also discusses promising research on fermented foods, specific bacterial supplements, mushroom extracts, and fasting approaches as complementary strategies to enhance cancer treatment effectiveness while reducing side effects.