Cancer is a disease that disrupts the body’s genetic composition, causing instability in the genome. The immune system plays a crucial role in diminishing the effects of cancer, making immunotherapy a frequently utilized therapeutic approach for individuals dealing with various forms of cancer. The efficacy of immunotherapy relies on various factors associated with patients’ lifestyles and overall health conditions. Furthermore, existing evidence highlights the importance of making lifestyle modifications. Similarly, dietary and other behavioral changes have been demonstrated to successfully induce beneficial health outcomes in cancer patients during immunotherapy. The substantial and expanding body of evidence supporting the incorporation of various factors into lifestyle modifications has the potential to enhance the formulation of lifestyle guidelines in various contexts, as elaborated upon in the forthcoming chapter.