From a mechanistic standpoint, the improvement in treatment response without increased toxicity supports the biological concept of differential stress resistance and stress sensitization. CR reduces systemic insulin and IGF-1 levels, which downregulates pro-growth pathways, such as PI3K–AKT–mTOR, and activating stress responses, including AMP-activated protein kinase pathways and autophagy
7. These shifts lead to cell-cycle arrest, better oxidative stress resilience, and improved cellular repair in healthy tissues. Conversely, cancer cells, defined by constant oncogenic signalling and poor stress response, cannot activate protective mechanisms, making cancer cells more vulnerable to damage from chemotherapy and radiotherapy. This difference helps explain the positive treatment outcomes observed in studies, even when patient-reported toxicity and QoL change little.